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Author Topic:   New Yamaha F70 Four-cycle
frontier posted 11-17-2010 03:20 PM ET (US)   Profile for frontier   Send Email to frontier  
The new F70 Yamaha 70 HP four-cycle outboard has now been on the market for quite a while. What are some real world data--speeds, gas usage, low end torque, noise--from those of you that have it on a classic 17 hull? Any problems?
zotcha posted 11-17-2010 08:44 PM ET (US)     Profile for zotcha  Send Email to zotcha     
Saw my first on a very, very late model Carolina Skiff. Did not get to speak to owner but looked larger than my 2005 and 2009 F60's. I was on the phone and may have misjudged. zot. Sorry for no assistance.
tedious posted 11-18-2010 08:08 AM ET (US)     Profile for tedious  Send Email to tedious     
I put an F70 on my 15, completed the install in September, and have only been able to get out a couple of times. I'm still working on finding the right prop, and it's on a 15, so I have nothing for you that would be meaningful to performance on a 17.

From a limited sample, gas usage is very good - dramatically better at lower speeds than the Johnson 70 the F70 replaced - that's as expected. Quietness is good, but not great, at least in a 15 where you sit very close to the motor. I guess I was expecting it to be as quiet as my 2005 F200, which is virtually silent at idle and low speeds; that was probably naive. With the F70, you do hear some mechanical noise at low speeds - someone described it as a sewing machine sound, and that's about right. Still, the noise level is far less intrusive than the old Johnson 70, again as expected.

The standard modern EFI attributes of instant starts, reliable idle, and good throttle response are all there. Low end torque seems good, but again I am still finding the right prop, so a complete evaluation of that will have to wait.

No problems yet, and hopefully not for a while.


L H G posted 11-18-2010 06:39 PM ET (US)     Profile for L H G    
I'd be curious to see how it runs against the Merc 60 EFI 4-stroke, since both are built on the same block. Boston Whaler's 150 Sport performance data, using the 60 EFI could be used. Maybe 2 mph better?
jimh posted 11-18-2010 10:34 PM ET (US)     Profile for jimh  Send Email to jimh     
Whoa---How did the completely new Yamaha F70 turn out to be using the same engine block as the Mercury? I need to hear this story told slowly and carefully.
L H G posted 11-19-2010 01:20 AM ET (US)     Profile for L H G    
Jim - Check the bore, stroke and displacement of both, then report back, slowly, the specifications you find for each. Yamaha claims to squeeze the extra HP from the same block by the use of dual overhead cams, instead of the SOHC, which I do not doubt.

Did Mercury knock off the Yamaha short block design, and copy their block design and specs, or did Yamaha knock off Mercury, and copy their design and specs? Or is it an incredible engineering co-incidence from Continents away? Or are both short block assemblies made in the same plant?

Where are the infringement lawsuits for knocking off someone's engine block design? After all, Yamaha and Mercury hate each other. I have learned that here.

I really wish someone would give the answer here to these specific questions.

But nobody can, since absolute confidentiality agreements evidently must exist. But ask a dealership that works on both brands, like I have.

Tom W Clark posted 11-19-2010 01:34 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
[ chuckle ]

This should be good.

jimh posted 11-19-2010 09:18 AM ET (US)     Profile for jimh  Send Email to jimh     
From what little I know--I just carefully read the product literature--it seems that the new Yamaha F70 uses a single overhead cam (not double overhead cam as mentioned above), however it is distinguished as having four valves per cylinder. The 50-HP and 60-HP variants must have just two valves per cylinder.

The 996-cc displacement is the same as the 50-HP and 60-HP variants, so it is reasonable to infer that the bore and stroke among the three models are the same. I don't see those dimensions listed on the Yamaha website, and therefore I cannot know if they match up with other engines.

Mercury says their 60 EFI has 995-cc of displacement. They list the bore and stroke as 65-mm x 75-mm.

Perhaps both the Yamaha and Mercury outboards evolved from the early joint-project four-cycle engine. Some time ago--the precise epoch escapes my memory--there was a five-year co-manufacturing agreement during which Yamaha and Mercury collaborated to make a four-cylinder four-cycle outboard in the 40 to 50-HP range. After the five year deal expired, both continued to manufacture the engines on their own.

The secret on-going collaboration theory has been proposed many times, but actual evidence has been non-existent. As I have suggested many times before, evidence in support of this theory could begin with two photographs of two engine blocks, one Yamaha, one Mercury, in which some unusual detail of the casting was shown to be identical. This might be an inference that a common manufacturer made the block, but it would not really prove it. It could just as easily be that each casts their own, using a common mold.

My nearest Mercury dealer is also a Yamaha dealer, but, alas, the economic slow down of 2008 drove him to close his showroom area and cease selling new boats. He now focuses his business on engine repairs, and having sold Mercury outboards and Mercruiser sterndrives for 50 years, he does not lack for work. But I can't easily find the Yamaha F70 and a Mercury 60 EFI sitting next to each other. If I could, I would be pleased to remove the cowlings and inspect them for similarities. I do invite anyone else to do the same and report herein.

Keeper posted 11-19-2010 12:07 PM ET (US)     Profile for Keeper  Send Email to Keeper     
Thanks Gents.
You guys have a ton of wealth and knowledge.
You paint a great picture.
I have some prop testing to look forward to this spring!
I dig it !
Thank you!
Tohsgib posted 11-19-2010 12:31 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Keeper for decades a 70hp(any brand) on a 15' ran a 2" larger pitch than if on a Montauk. I assume that is a good starting point. As the 70 4 stroke and 2 stroke Yamahas have the same gear ratio I think a 17" stock prop or a 15" stiletto should do the trick.
Tohsgib posted 11-19-2010 12:44 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Maybe this helps bulletin_4stroke_midthrustjetport_gyt3_sa9d6d.tmp.pdf
JMARTIN posted 11-19-2010 02:28 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
I got a F70 on a 15 Sport, but do not have any "real" figures. Looking at the performance bulletin, I am skeptical of their figures.

The comfortable cruise spot for me is 3800 RPM and I will bet I am going faster than 23 mph. I am guessing 25 to 28 mph at 3800 rpm and over 40 mph at 6300 rpm.

It has the Yamaha K series 17 prop on it.

I should take her down to the lake with my wife's new Tom Tom and see just what it does.


Peter posted 11-19-2010 02:49 PM ET (US)     Profile for Peter  Send Email to Peter     
At 3800 RPM you should be going about 24 MPH and at WOT about 41 MPH with the 17 K-series prop. As a comparative datapoint, I ran the 19 K-series prop on my 70 2-stroke. WOT was 5900 RPM at approximately 42.5 MPH. 24 MPH cruise was about 3400 RPM.
JMARTIN posted 11-19-2010 02:57 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
I was able to hit 6300 rpm with the 17, which is what the riggers wanted.


Tohsgib posted 11-19-2010 03:12 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
So you are running a K17 on a 15' so a k15 or equiv. should be correct for a 17'.
fishgutz posted 11-19-2010 04:45 PM ET (US)     Profile for fishgutz  Send Email to fishgutz     
Comparing this: bulletin_4stroke_midthrustjetport_gyt3_sa9d6d.tmp.pdf
to this: EnginePerformance/204624_EnginePerf.pdf
I wonder why the Yamaha F70 is no faster than the Mercury 60 BF.

10 extra horsepower and NO extra speed. No better performance at anything, really.

In my own opinion I have always believed if you want to go fast you need to get a Mercury. Seems to me from past performance charts that Suzukis were pretty fast, too. Evinrude and Yamaha were slowest and Honda depended on the models, some were faster some were slower. The only one that can't be compared is Tohatsu. Their old motors seemed to be dogs. They have some new models for 2010 Particularly a new 75 HP direct injected 2 stroke. They don't publish any performance bulletins.

fishgutz posted 11-19-2010 04:48 PM ET (US)     Profile for fishgutz  Send Email to fishgutz     
Let me qualify one point. I am generally talking about 40 to 90 horsepower as those are the motors I usually compare because of the boat I have and the boat(s) I may have in the future.
L H G posted 11-19-2010 06:00 PM ET (US)     Profile for L H G    
The joint venture Mercury/Yamaha 50's were 1993-2002 model years, 10 years, not 5. This new 60.8 CI block showed up in 2003, for both the Yamaha 60's and Mercury 60's, both showing 60.8 cubes, and the identical bore and stroke.

In the old joint venture Mercury manufactured all of the short blocks for both, and Yamaha manufactured all of the cylinder heads and cams for both. They they took these powerheads and built their own full outboards. In 2003, Mercury claimed that the 40-60HP engines were now 100% Mercury built and manufactured, so now Mercury is doing their own heads & valve train, no longer buying from Yamaha.

So it certainly could be possible, Mercury is STILL making the newer displacement short blocks for Yamaha too. Then they are shipped to Japan and China for inclusion in the outboards of both companies. Even though the short blocks are the same, maybe the valve train and other components like gearcases are the reason the Mercs are now faster. In tests of the 50HP versions they have been shown to be faster also.

I am surprised, however, to see that the new Yamaha 70 is no faster than the Merc 60. That makes the Mercury a "best buy".

seahorse posted 11-19-2010 07:21 PM ET (US)     Profile for seahorse  Send Email to seahorse     
the new F70 Yamaha has a 65mm bore and 75mm stroke.

One thing that is different is the sparkplug is a LKR7E where the 50 and 60 use the traditional DPR-6.

Peter posted 11-19-2010 09:43 PM ET (US)     Profile for Peter  Send Email to Peter     
I am surprised, however, to see that the new Yamaha 70 is no faster than the Merc 60. That makes the Mercury a "best buy".

No need to worry about details such as the comparative boats are made by two different manufacturers, Key West and Boston Whaler, and that the Key West has a max HP rating of 80 HP and the Whaler only has a rating of 60 HP.

Tom W Clark posted 11-19-2010 10:17 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Uh, the question was about the Yamaha F70's performance, nothing more. John Martin repowered his Sport 15 with one this summer; I was hoping he would chime in here.

As to Larry's crazy claim, an outboard with the same bore and stroke is not very strong evidence that Yamaha is paying Mercury Marine to produce outboard motor short blocks in the USA and mail them to Japan for use in an all-new Yamaha outboard motor, but then, Larry squandered his credibility years ago, so I think we drop this lie in the trash.

jimh posted 11-19-2010 11:00 PM ET (US)     Profile for jimh  Send Email to jimh     
Generally it only makes sense to ship high-value finished goods great distances. It makes no sense at all to manufacture and assemble all of an engine in Japan, but buy the least-complex component, the engine block casting, from a vendor who is 14,000 miles away. Yamaha would have to pay to ship the heavy and bulky component 14,000 miles from Wisconsin to Japan, turn it into finished goods, and ship it back 14,000 miles to Wisconsin to be sold. When you also consider that four Yamaha products, the 40, 50, 60, and 70-HP engine are using this component, the notion that they would import that simple component from a vendor 14,000 miles away becomes even more unbelievable. When you consider that Yamaha is able to produce or source all of the other engine blocks in the many outboard motors it makes without buying them from Mercury, an even greater strain is added to credulity. Other costs, like customs, import duty, currency conversion rates, and transshipment from harbor to factory, also add to the uneconomical approach to buying a simple casting from someone 14,000-miles away. However, none of this can rule out that Yamaha and Mercury, in spite of their public confrontations where they sue each other, and in spite of absolutely no mention of this anywhere in any literature, blog, or website except here from Larry, could possibly be maintaining a secret co-manufacturing agreement to collaborate on this particular new Yamaha F70 engine.

As part of the careful and slow reading I do on topics like this, I would like to present an excerpt from

Outboard Engines From Japan
Investigation No. 731-TA-1069 (Final)

and to it I have added emphasis on a couple of points which are in complete support of my point of view and which contradict Larry's statements.

Mercury entered into a co-development program with Yamaha in 1993 for the production of small (9.9 to 50 horsepower) 4-stroke engines, in which the partners each agreed to “take the lead on the design and development of different size powerheads.” For each powerhead designed under this arrangement, manufacture of its specific components was allocated between the two partners “*** for the powerhead.” The company responsible for designing the powerhead also negotiated “***.” Mercury producer questionnaire response, section I-5. This arrangement not only reduced production and development costs for each partner, but also gave Mercury timely
access to 4-stroke engine production. Conference transcript, pp. 58-59 (Dempsey). Engines developed under this agreement were subject to a 5-year minimum co-manufacture window, after which time Mercury chose to produce some of the engines on its own; other engines are still being co-produced. Conference transcript, pp. 67 and 72 (Davis). The first powerhead to be developed separately was the 50 HP engine, which both Yamaha and Mercury now produce independently. The 9.9 HP powerhead is also no longer part of the agreement. The two powerheads remaining subject to the agreement are the 25 HP and 40 HP powerheads. Hearing transcript, pp. 80-81 (Davis).

Let me repeat the two points I emphasize above:

The co-manufacturing agreement was for five years minimum, and Mercury broke it off after five years to make some of the engines on their own. Yes, they did continue to make some engines together after five years, but there is no specificity. Also, this report was issued early in 2005, and its investigation covered up to 2004. So when the report mentions that there was some on-going co-manufacturing, it is referring to the status of the Yamaha-Mercury co-manufacturing at least six years ago. This was long before the relationship between Yamaha and Mercury turned ugly. After Mercury initiated their complaint with the USITC, Yamaha was not exactly their bosom buddy. Yamaha stopped selling Mercury critical components for the production of their four-cycle engines, and Mercury had to sue Yamaha to compel them to sell Mercury these finished goods--the assembled power head for the 90-HP four-cycle--which Mercury was desperate to have to stay in business in that product segment.

The first engine built in the co-manufacture was the 50-HP--whose engine block is basis of the new Yamaha F70--and which according to the investigation "both Yamaha and Mercury now produce independently." It hardly seems possible that Yamaha would produce the 50-HP version independent of Mercury but then resort to making the F70 new engine with a Mercury block.

Incidentally, in the 180-page document, the paragraph I quote above is the only instance of the word "co-manufacture."

Now I am not sure that the printed and published document of the USITC issued by a government agency is sufficient to stop the true believers in this secret deal where Yamaha's critical mid-range four-cycle engines are all being built on an engine block made by Mercury, but I think it does tend to make that secret deal seem even more unlikely and more difficult to believe in.

Tohsgib posted 11-20-2010 12:58 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Tom...JMARTIN did chime in.
Tom W Clark posted 11-20-2010 01:04 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Oh, I missed that. See what these silly topic diversions can do?
L H G posted 11-20-2010 01:55 AM ET (US)     Profile for L H G    
Jim incorrectly states: (and I am substituting the word "China" wherever he used "Japan" and the word "Mercury" wherever he used "Yamaha" for my point)

"Generally it only makes sense to ship high-value finished goods great distances. It makes no sense at all to manufacture and assemble all of an engine in China, but buy the least-complex component, the engine block casting, from a vendor who is 14,000 miles away. Mercury would have to pay to ship the heavy and bulky component 14,000 miles from Wisconsin to China, turn it into finished goods, and ship it back 14,000 miles to the Edgewater FL plant of Boston Whaler to be sold. When you also consider that three Mercury products, the 40, 50, and 60HP engines are using this component, the notion that they would import that simple component from a vendor 14,000 miles away becomes even more unbelievable."

AN UN-INFORMED BUSINESS COMMENT. That is exactly what Mercury has been doing quite successfully with the 40-60 stroke EFI's for several years now. If Mercury does it, Yamaha could too. So scratch that argument.

For years, as part of that Joint Venture agreement, Mercury also built Yamaha's complete 25HP engine and furnished the 3 cylinder modular short block for the 30HP engine. When Mercury stopped making these models for their own line, and switched to the new Mercury/Tohatsu Joint venture engines in 25 and 30 HP, Yamaha was left with no offerings in the 25 and 30HP range for several years. Check their catalogs and note the HP gap from 15 to 40. Not too long ago, they finally got their own version of these engines designed and manufactured on their own.

Nobody has yet told me why the blocks of the two brands of 4-stroke mid-range engines are identical. Thanks to Seahorse for giving us the bore and stroke of the Yamaha models, proving it is identical to the bore and stroke of the Mercs. I don't know how this happens, but I sure would like to know. But we do know from the very beginning of this series of engines, the two companies worked together.
The Mercury/Yamaha block of 2003 to current, incidentally, is different displacement than the earlier Joint Venture 50HP block.

fishgutz posted 11-20-2010 08:59 AM ET (US)     Profile for fishgutz  Send Email to fishgutz     
Wow, this thread got derailed. How about getting back to discussing performance of the new F70 by Yamaha. I know Frontier wants to know specifically about the performance on a Classic 17 but any performance reports could be helpful.
Peter posted 11-20-2010 12:24 PM ET (US)     Profile for Peter  Send Email to Peter     
"Wow, this thread got derailed."

Yup. The Maveric from the Mercury Marketing Department is a master at diverting attention away from other brands of outboards.

Waterwonderland posted 11-20-2010 10:31 PM ET (US)     Profile for Waterwonderland  Send Email to Waterwonderland     
Derailed, yes, but as a spectator it is fun to watch the p-ssing match unfold.
jimh posted 11-21-2010 12:04 PM ET (US)     Profile for jimh  Send Email to jimh     
It's Larry against the world, and in this case the world includes the published testimony of outboard manufacturers themselves as reported in the United States International Trade Commission final report.

I cannot argue that Mercury makes its own 25-HP four-cycle engine in the U.S.A. It was rather ironically pointed out in the testimony of the USITC investigation that this particular four-cycle engine was the only four-cycle engine made by Mercury entirely in the U.S.A.. However, Larry has, without the tiniest shred of evidence, stretched this fact into a completely new one, his often-repeated claim that Yamaha actually gets the crucial components of the F70 engine from Mercury. In support of this one cannot find anyone on the record other than Larry. While I have no problem with Larry's testimony on this, Larry cannot corroborate himself.

For corroboration of my information, I use the published testimony of the outboard manufacturers who make these motors. I will leave it to readers to decide which information is more credible.

Although Larry has tried to refute my argument by pointing out that Mercury actual successfully follows the uneconomical practices I cite--sending unfinished goods a long distance to be finished and then sent back--I can simply refute that by pointing out the value of Brunswick stock (sunk) and Mercury Marine's well known reliance of subsidies from Wisconsin's taxpayers to remain in business (bail-out).

Another simple explanation for the Mercury practices: since they are already shipping thousands of outboards from Asia, perhaps they thought they could make use of the empty shipping containers to send a few parts back for assembly.

I also think that wages in the Far-East have probably risen. Shipping costs have risen. And concern about quality has risen. All of these factors will tend to reduce the economic advantage of assembling in the Far-East components that are initially produced 14,000-miles away.

L H G posted 11-22-2010 03:59 AM ET (US)     Profile for L H G    
Well, I was hoping someone could tell me how the Yamaha F70 and Mercury 60 EFI could be running on the indentical block, but it is apparent no one here has enough information to know the answer.

I'll have to turn to other more knowledgeable sources. I'll report back.

fishgutz posted 11-22-2010 08:37 AM ET (US)     Profile for fishgutz  Send Email to fishgutz     
If my memory serve me correctly, back when 4 stroke outboards first came out by Mercury and Yamaha they made very similar if not identical motors, shared technology and shared parts. Now that they have completely split it is most cost effective to still use the original designs rather than revamp all the castings. MW Marine (Largest dealer in Wisconsin) started carrying Yamaha when they started producing 4 stroke motors. They showed me a Mercury and a Yamaha with the covers off side by side and the engines were identical.

Not all Mercury or Yamaha parts are made IN the Mercury or Yamaha plants. Just as an example, when I worked in Milwaukee we'd go into small factories for fire and rescue calls that were making parts for Mercury, Evinrude and Chrysler/Force outboards (among others that were unidentifiable).

So I'm sure many parts are the same or at least bought from the same suppliers even today.

jimh posted 11-22-2010 10:00 AM ET (US)     Profile for jimh  Send Email to jimh     
Larry--I know how you feel. You ask for credible information and you get nothing but wild conjecture. Happens all the time here. I hope you find the definitive answer on what motor is better, a Yamaha F70 or a Mercury 60-HP. I know what way you're leaning, though.
Peter posted 11-22-2010 10:41 AM ET (US)     Profile for Peter  Send Email to Peter     
Yamaha's parts diagrams show that the F50 and F60 share the same part number for the cylinder block assembly and crankcase assembly. Further, according to the parts diagrams for the F70, it does not share the same part number for the crankcase assembly or cylinder block assembly with the F50 or F60.

It's unlikely that this motor's cylinder block makes a round trip from here to there and back to here (or there or anywhere else). In fact, other than here, I don't think they go anywhere else because everywhere else they still use 75 HP Yamaha Enduro 2-strokes for where an F70 could be used. So there you have it, the definitive answer to the implied question from the Maverick is that the F70 has no Mercury DNA in it. ;)

Tohsgib posted 11-22-2010 02:14 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Look at it this way, copying is the highest form of flattery or however the saying goes. Yamaha copied 75% of their engines from the start, why stop now? Lastly the internals are not inhouse stuff. If Yamaha was happy with their joint venture engine, why not continue to make it after the venture ended, if allowed by law. If they make their own block and heads now but still use the Wiseco pistons and XYZ rods along with the ABC bearings and JFK crank and same gasket kit used on the Merc 60, tooling and parts costs will be minimized. For cars to do this it is much easier as they sells millions of engines per run. Outboards may sell only a few hundred thousand; retooling is like an organ transplant.
Tohsgib posted 11-22-2010 02:25 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Lastly I don't know what the big deal is. They do this in the car and motorcycle industry all the time and are blatant about it. Kawasaki motorcycles like the KLR50, KX65, 85,100, etc are rebadged Suzukis or vice versa depending on the model. They change the plastics and the emblems. Scary thing is sometimes the parts are different prices. On my Suzuki JR50 it was 25% cheaper to buy the brake lever from Kawasaki--same lever down to the color.

Cars: Suzuki pickup is a rebadged Nissan Frontier. The new Hyundai's are using Mitsubishi engines. Dodge and Mitsubishi did this for decades along with GM and Toyota/Suzuki rebading their cars. Saab uses GM engines and Opel platforms. Cadillac and Corvette are using same chassis, suspension and engines. Jeep uses a Mercedes owned engine with a Chrysler transmission, and owned by Fiat? Ford uses International or inhouse engines yet they own a majority stake in Cummins which are used in Dodge trucks? Who knows? Who cares?

Keeper posted 11-22-2010 07:29 PM ET (US)     Profile for Keeper  Send Email to Keeper     
EXACTLY !!!! Thank you.
jimh posted 11-23-2010 08:44 AM ET (US)     Profile for jimh  Send Email to jimh     
Regarding use of common parts in the automobile industry, I can add this anecdote. Many years ago a friend of mine had just graduated with a degree in electrical engineering. He went to work for an automobile manufacturer, not one of the big three. One of his first assignments was the dome light for a new model coming out. An older, more experienced engineer gave him some help. They got in their car and drove off to several Chevrolet, Ford, and Chrysler car dealerships. They looked at several dozen different cars, until they found one that had a dome light they liked. Then they went to the parts counter at that dealership and bought a replacement dome light. That part became the prototype for the dome light in the new car their company was building.
Tohsgib posted 11-23-2010 12:09 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Well we know he was not designing a convertible ;)

The old Fords with the big chrome domelight and the 2 small maplights built in was the BOMB!

tedious posted 11-24-2010 07:31 PM ET (US)     Profile for tedious  Send Email to tedious     
L H G, one thing I'm missing in all this is why you care so much whether the Merc and the Yamaha (whether 50, 60, or 70) share the same block casting. Everybody else seems to know some history that I don't (and I confess I didn't read every word of this long thread) so forgive me if I get this wrong, but the only thing I can figure is that you think Yamaha is trying to sell inferior Mercury blocks to an unsuspecting public. Maybe you bought a Yamaha, found out the block was made by Mercury and somehow feel this is some type of scam? If so, I wouldn't worry - the engine block casting itself is only a small part of the equation, and the electronics, induction system, and valvetrain are just as important. And I don't really believe Mercury blocks are inferior in any way - I don't know why you'd think that.


fishgutz posted 11-25-2010 09:39 AM ET (US)     Profile for fishgutz  Send Email to fishgutz     
I'm kind of with LHG on this one although we are all off topic. No one has a definitive answer as to why Mercury and Yamaha use a similar if not same block.

I have a sort of explanation in my earlier post, yet not definitive.

Also I don't believe the 70 will be that much faster (if faster at all) than the Mercury. No real definitive answer if you look at performance reports. Just a slight trend of Yamahas being a bit slower.

L H G posted 11-25-2010 01:01 PM ET (US)     Profile for L H G    
Per "tedious" and his post addressed to me:

"And I don't really believe Mercury blocks are inferior in any way - I don't know why you'd think that."

I don't and I never said that. Currently I own eight Mercury outboards, everyone being manufactured in Fond du Lac between 1984 and 2006. Need I say more?

If the Yamaha F-70 has a Mercury manufactured short block, it could be a great engine. If the Yamaha F-70 has a Yamaha manufactured short block, it could also be a great engine. Same for the F40. F50 and F-60.

seahorse posted 11-26-2010 09:59 AM ET (US)     Profile for seahorse  Send Email to seahorse     
Direct from Yamaha:

Mercury hasn't done any casting work for Yamaha since the anti-trust lawsuit several years ago. Since then, all work for each other was ceased. The 60-cubic-inch block, as are all Yamaha blocks, are cast by Yamaha in Japan and have been for quite some time now.

tedious posted 11-26-2010 02:06 PM ET (US)     Profile for tedious  Send Email to tedious     
Thanks L H G, guess I got that wrong. However, I'm still confused as to why the question of Mercury and Yamaha sharing blocks is so important to you.

Fishgut, I've learned that performance comparisons are tricky - it's hard to find data that changes only one variable, which of course is the only truly valid means of comparison testing. Comparing two different motors on two different boats is unhelpful - if there is a difference, you'll never know if it's the boat or the motor.

I went through the effort of comparing various Yamaha products in this post here:

- see the table about 10 posts from the end of the thread. But even there, even though it was at least on the same boat, the weather was different, the total weights were different, and they don't seem to have done a great job propping the 70TLR.

I'd expect the Merc EFI 60 Bigfoot to perform about the same as the Yamaha T60 - both large gearcase motors. And you're correct, the performance differences between the T60 and the F70 are not all that great, only about 4 MPH in top speed. I did look at both the Mercury and Sundance sites to see if there was any data with a Mercury product on the Sundance boat, but no joy.


jimh posted 11-27-2010 11:49 PM ET (US)     Profile for jimh  Send Email to jimh     
Perhaps we can finally put to bed this persistent and imaginative notion that Yamaha has to have their engine blocks made by Mercury and shipped 14,000 miles to them in Japan.
towboater posted 11-28-2010 04:25 AM ET (US)     Profile for towboater  Send Email to towboater     
I purchased 2010 F70LA 6CJL 1001284 with tiller handle on 6/29/10 as backup motor for heavy 20 ft alum work skiff while the primary motor (Merc 200) got a new powerhead.

I dont have any GPS data, during the 3 weeks of 4 hr per day service, the F70, stock alum Yamaha prop would bring the work skiff on step with 2 persons and 40 gal gas.
Most of the time it packed around 6 big adults and their gear back and forth between dock and bridge piers. I never did weigh the skiff but it pulls and feels very close to the same weight as my CPD 18 on a trailer. Im sure it would plane a 18 ft Outrage pretty easy.

F70 did a LOT of shifting and plowing thru the water WOT.
Id guess they made an average of 15 landings per day.
The engine never missed a beat. Started right up on cold morings every time. Nothing went wrong. It is VERY QUIET and sips fuel compared to the big block.

Sorry I cant add much more data cept it is a great engine I would recommend to anyone. Only comes with 20" shaft at the time I purchased it. The 4" setback of CMC jackplate had enough reach to lower to accomodate 25" transom and still tilt ok with the tiller handle. Been sitting in my shop for 3 months now. Merc 200 runs great. 57 mph on same hull. I will be offering F70 for sale thru CW Market soon. Have all warrantee info, expires July 2013.

renoduckman posted 02-06-2011 02:50 PM ET (US)     Profile for renoduckman  Send Email to renoduckman     
Interesting thread, but it got off topic a bit.

I have been dreaming of a repower on my 74. From what i have read and my experience it seems that the F70 should be a good fit for a fisherman like me. I have been looking at the best bang for the buck in my situation. I have been milking the last life out of the old 80HP Merc.
I appreciate any more info on this motor as a possible repower. Joe

jimh posted 02-06-2011 05:13 PM ET (US)     Profile for jimh  Send Email to jimh     
"Interesting thread, but it got off topic a bit."

Threads often get dragged off topic when some participants enter the thread in order to impose a certain agenda on the discussion. However, I think we have established that there is no basis at all for that particular sidebar discussion, and I hope that this will be the end of that topic for all time.

I am afraid that in the three months that have elapsed since the discussion began, those of us in the Northern part of the United States have more or less ceased our boating activities, so I would not expect that too many have new information to add about the performance of the new Yamaha F70 four-cycle engine on their Boston Whaler boats, unless some of our Southern cousins can chime in.

Tohsgib posted 02-07-2011 11:03 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
duckman...look at suzuki as well if you want 70-90hp. Also look at 60's which will give you close to the 70's performance but easier to find cheap.
renoduckman posted 02-07-2011 02:39 PM ET (US)     Profile for renoduckman  Send Email to renoduckman     
Will do. IT just seems to me that the 70 should be a great size for the boat. I have done some looking at the 60hps. Not sure which one is a better buy. Joe
Tohsgib posted 02-07-2011 02:49 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
My bud has a 60 suzuki on his Montauk and I had the 70. We both swing the same prop because his redline is 5300 and mine is 5800 so our cruise speed is identical. The only difference was about 4-5mph at top end(38-39 vs 34-35). If I could save $1000+ over a 70 it would makes sense but resale might beg to differ about that grand down the road. My Suzuki weighed 359lbs so don't worry about the "weight" issue that much. The new 70-90 Suzukis are 341. My big concern with the F70 is the 6300 redline. This to me means a cruise speed in the 4500 compared to 3900 with an engine that redlines lower. I know it is relevant but it is also psychological. Kinda like my wife's Miata that ran 5k+ on the highway....thing was screaming but still got 30mpg.
renoduckman posted 02-07-2011 06:26 PM ET (US)     Profile for renoduckman  Send Email to renoduckman     
Yes the weight issue has me concerned. That is the reason i have looked at the 60hp. Id like to ride in a boat with a 60hp. While i am a fisherman, id hate to come up underpowered. I normally fish at about 5000 feet, so there is that issued to deal with. I know that that is normally a prop change. Joe
Tohsgib posted 02-07-2011 07:18 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Water depth means absolutely nothing if it is over your head :)

Max "recommended" weight is 410lbs. You will not find a 90hp today that breaks that weight barrier.

WT posted 02-07-2011 07:28 PM ET (US)     Profile for WT  Send Email to WT     
I think he means the 5,000 feet is the elevation in which he boats not water depth. :-)


renoduckman posted 02-07-2011 07:56 PM ET (US)     Profile for renoduckman  Send Email to renoduckman     
Yes i fish at 5k elevation. You do get some power loss but i think most of its corrects with prop change? Joe
tedious posted 02-08-2011 08:32 AM ET (US)     Profile for tedious  Send Email to tedious     
BS, in your previous post you stated: "My big concern with the F70 is the 6300 redline. This to me means a cruise speed in the 4500 compared to 3900 with an engine that redlines lower."

Many modern outboards redline at 6000 RPM. I am not sure why you think the F70's increase of 300 RPM at redline would mean an increase of 600 RPM (4500 vs. 3900) at cruise.

If you go back to the link I posted earlier ( and look at the table I created (8 or 9 posts from the end) you'll see that on that particular boat, the F70 gave a cruise speed of 23.4 MPH at 4000 RPM. The old 2-stroke 70TLR had a similar speed at 3500 RPM, which would be better, but it also had cruise MPG of only 6.26, compared to the F70's 9.36 MPG.

I hope to soon get a GPS that can link to my F70 to get fuel flow, and then if I can get my 15 out from under the huge mound of snow in my backyard, we may be able to have some data from an actual Whaler.


Tohsgib posted 02-08-2011 12:46 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
My 115 redlines at 6k and my "good" cruise is about 26mph at 4200. I am "assuming" this would now be 4500 if I redlined at 6300. My 70 Suzuki 4stroke redlined at 5800 and I maxed out at 5650 so my cruise was about 38-3900 at 26mph. I have found the boat is more efficient at the 25-28mph range than at lower speeds. Please keep us posted what you find out in "real" data down the road. Like Tom Clark posts with his boat, his best economy is at 32-33mph, not slower like most people assume. These new engines do not care that they are running higher RPM's nor does it wear them out quicker. We as boaters are just in that mindset from the old days where the lower the rpm's the better the economy and it is a hard habit to break. With a 13 or 17 this may be true because once the boat is on plane it just scoots along. As long as your bow is flat the engine is not working that hard.
Peter posted 02-08-2011 01:36 PM ET (US)     Profile for Peter  Send Email to Peter     
The F70 is essentially a T60 with an extra 300 RPM at the top. I bet that the power curve of a T60 and an F70 between 0 and 5500 RPM is imperceptably different and the extra 10 HP comes to play in the last 500 RPM for the F70. How many folks run their motors at 5500 RPM for any length of time? Not many.

Given that most of the time you'll probably run the motor at 4000 to 4500 RPM, you'd probably better off saving a buck or two with the T60 for a Montauk.

dgoodhue posted 02-08-2011 01:37 PM ET (US)     Profile for dgoodhue  Send Email to dgoodhue     
Cruise speeds/RPM comaprisons can be dependent on the Hull.

My 15' doesn't like to cruise at 20mph. I know don't know the exact speed that is but at 3300-3400 rpm is about the lowest rpm my boat will stay on plane, and I often have to play with the throttle. With 70hp I am well beyond the planning speed affecting my cruise speed. My boat cruises at 27mph @ 3800rpm, 31mph at 4000rpm, 34mph at 4200rpm with 6000rpm redline 3 cylinder 60/70 hp Evinrude. At redline it does 45mph. When I when up a 2" Pitch, my redline RPM dropped 500 rpm and my cruise speeds gained 2 mph.

If I had a Yamaha 70hp propped to 6300rpm, I don't imagine my rpm would be all that much higher in cruising around. At the same RPM, I would expect maybe 1 maybe 2mph drop or about 150rpm increase of cruise rpm to reach the same speeds (assuming the same brand/model of proppeller).

Now if this was on a difference larger boat where 70hp put the motor operating range closer to the planning speed. I can see the higher RPM affecting the cruising speed in that situation. (I am not sure if this would be the case with Montauk or not.)

Tohsgib posted 02-08-2011 02:52 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
This is about a Montauk so I imagine the prop would be 2" smaller in pitch and cruise would be much slower at the same RPM. Top speed would also be about 20% slower as well. I agree with Peter about the difference between the 60 & 70hp. For most it would be a moot point. I have seen a couple people with the 140 Suzuki on the same boat as mine and there is not much difference in top end either compared to MY 115. My 115 might also be "hot" compared to others but no way to compare.
tedious posted 02-08-2011 04:01 PM ET (US)     Profile for tedious  Send Email to tedious     
Dave, you make a good point (and I think BS is making the same one) that the cruise speed of a motor is more critical when it's closer to the minimum planing speed of the boat. With a motor at the high end of the HP range for the boat, the cruise speed will be higher than it would be with a less powerful motor. So with the relatively light 15 and a 70 (classic 2-stroke or newer 4-stroke) the boat is going to get its best mileage (which is the definition of cruise speed, right?) running fast and flat, just scooting along. For a Montauk, the 70 would be about 2/3 the maximum rating, so you'd expect relatively low cruise speed at a relatively high cruise RPM.

I think that's an argument to put the biggest motor possible on every boat, right?


Tohsgib posted 02-08-2011 06:02 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Not really. I was VERY happy with my 70 suzuki on my Montauk. I think the 60 would be fine as well. We were just commenting on the high rpm range of the new F70 and that it might cruise higher than typical because of it. Kinda like those SeaDoo jet boats, they redline at like 10k and you cruise around with 2 of them behind you screaming at 7k all day....takes some to get used to.
Peter posted 02-08-2011 06:19 PM ET (US)     Profile for Peter  Send Email to Peter     
It still takes X HP to go Y speed. The bigger motor allows you to SLOW the engine speed down to make the X HP needed for the Y boat speed. Slower engine speed means a QUIETER, more relaxing cruise and longer engine life. It also means higher top speed to the extent there are the times when you need it. Also means greater load carrying capacity.

I'll bet the difference in engine speed at a 25 MPH cruise on a Montauk is at least 500 RPM less for a 1.6 or 1.7L 90 HP outboard than it is for a 1.0L 70 HP outboard.

Tohsgib posted 02-08-2011 06:41 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Again that is not true. I bet the 70 with a redline of 6300 is going to cruise at a MUCH higher RPM than my bud's Suzuki 60 4 stroke with a redline of 5300 at the same speed of say 26mph.
Peter posted 02-08-2011 09:41 PM ET (US)     Profile for Peter  Send Email to Peter     
Nick -- What is false about what I wrote? The prior generation 359-lbs Suzuki DF60 with the 5300 RPM redline was built on a 1.3-L (79 cubic inch) block. It's a BIGGER motor than the 1-L Yamaha F70 in two ways -- weight and displacement. Given that most 4-stroke motors are able to make 1-HP-per-cubic-inch-of-displacement, the old DF 60 was basically a detuned 80 HP outboard. The Yamaha F70 is a hyped up 60 HP motor.

You just like to argue. ;)

Tohsgib posted 02-09-2011 11:23 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Peter c'mon! Your explanation has NOTHING to do with what you wrote. He asked about hp ratings and range and maybe bigger was better and you explained why..."The bigger motor allows you to SLOW the engine speed down to make the X HP needed for the Y boat speed. Slower engine speed means a QUIETER, more relaxing cruise and longer engine life." As in the past you were referring to HP, not cubic inches. He was asking about hp, not bigger cubic inches. We have not been disussing cubic inches in this thread.

To better prove this you said "It also means higher top speed to the extent there are the times when you need it. Also means greater load carrying capacity." If you are serious about talking about cubic inches how on earth could a 60 do this over a 70?

Peter posted 02-09-2011 11:39 AM ET (US)     Profile for Peter  Send Email to Peter     
Nick -- See last line in my previous post.
Tohsgib posted 02-09-2011 11:39 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib the past except for a few certain engines and quite a few Mercs an outboard was built in say 3 differnt hp ranges but still had the same redline(OMC 90, 115, 140 @ 5500). This is true in what Peter says about the higher hp being able to slow down some and be quieter and more efficient yet when needed you will have a higher top end....absolutely true because the higher hp has to swing a larger prop to be within the 5500 redline it's 25hp less brother reaches as well. Mercury's 90 redlined at 5250, the 115 at 5500 and the 140 at 5750 so they all swung the same prop, higher hp just meant higher top speed.

TODAY however the hp is in the ECM and the redline with MOST 4 strokes. A 100hp Suzuki is rated for 5500, the 115 6k and the 140 6200. Going from a 100 to a 140 is NOT going to reduce your engine speed at cruise, make anything quieter or improve economy at say 4000rpm at 26mph because each engine has the same gear ratio and will swing the same prop and will need X amount of hp to move it 26mph. The ONLY thing the higher hp will do is give you a slightly better holeshot and top speed. The same boat with a 100 or a 140 will swing the same prop because the extra hp is needed to get the engine into it's higher redline.

So yes Peter I do like to argue...when I am right. I usually call Uncle when I am wrong ;)

Tohsgib posted 02-09-2011 11:41 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Peter--see last line in my previous post and implement it sometimes.
Peter posted 02-09-2011 02:50 PM ET (US)     Profile for Peter  Send Email to Peter     
Nick -- Your example is not big to bigger it is simply low to high.

I have some "bones to pick" with your analysis. First, the DF100 and the DF115 have a 6000 RPM redline according to Suzuki, not 5500 and 6000 respectively as you indicate. Let's stick to the published facts. The 140 has a 6200 RPM redline, just 200 RPM higher than the 100. All three outboards use the same 2.59:1 gearing.

With those facts on the table, the 140 will surely require a different, higher pitch propeller than a 100 on the same boat. The higher pitch propeller will reduce the cruise RPM.

Let's look at a hypothetical example of a DF 140 and DF100 on an Outrage 18 so we have some Whaler content. We've been informed in the past that a DF 140 is good for 42 MPH top speed. I'm unaware of anybody putting a DF100 on the Outrage 18 so we have to estimate what it would do based on the reported performance of a DF140. We can use the simple square root analysis S2 = (HP2/HP1)^0.5*S1 to figure that out. When you plug all the numbers in, the answer is the DF100 should be good for 35 MPH at 6000 RPM. What prop is needed for each motor to get them to their redline (assume 8 percent slip)? The CW prop calculator says almost 20 inches for the DF 140 and almost 17.5 inches for the DF 100. So now if we run the hypothetical Outrage 18s at 25 MPH, what RPM do each of the motors turn? Using the CW prop calculator and staying with the 8 percent slip, it says a few RPM shy of 3700 RPM for the 140 and almost 4300 RPM for the DF100. That's a 600 RPM difference for motors built on substantially the same platform. I know which motor I would be choosing and its not the one turning 4300 RPM at 25 MPH.

Even the DF 115, which should be good for 38 MPH on the Outrage 18, would need different propping than the DF 100 to reach its 6000 RPM according to the CW prop calculator. The CW prop calculator says the DF 115 will need a 19 inch prop. Unfortunately, Suzuki doesn't make propellers for these motors in 1.5 inch steps so either the DF 115 won't turn to the redline or it will over rev if the same propeller that the DF100 uses is used for the DF115.

Your example is much like the OMC example you previously mentioned.

Ready to cry "uncle"? ;)

What's this got to do with the Yamaha F70? Not much other than if I were powering a classic 17 hull, I'd probably chose the F75 over the F70 although I don't really like the weight of the F75 all that much.

Tohsgib posted 02-09-2011 03:35 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
I have some bones to pick with your calculator. First I was going to use the Df90 which is the same engine but I knew you would point out it was replaced with the 100(but the same as the 115/140) and has a 5500 redline. Again you are completely wrong because you are using a "calculator" and going all "hypothetical" here. I am using real world experiences gathered from me, here, and my friends who own the same boat/engines. First my 19' with a Df115 is running a 22" Stiletto at about 5900rpm and 40mph. The 140 DOES run the same prop and gets "closer" to the 6200 redline but top speed is not much higher for some reason. I ran the 20 and my redline was close to 6200. My boat is heavier than the 18 outrage so your 17.5 or even 20" prop is probably wrong again. My boat does about 26mph at 4200. The Df90 and the Df140 would do exactly the same at cruise because they would be running the SAME prop. Peter it takes years of running a boat with different engines, etc to come up with this can't hang out and be a "Crouch potato" and demand respect.

My Suzuki example is NOTHING like my OMC example. My OMC example shows different HP with the same redline. You would NEED a larger prop to run a 115 than a 90 on a 17 Whaler(17 vs 19 SST). How would I know this...uh I have owned 8 17's. With a DF90 or DF115 on a 17 you would run the same prop...probably a 24" Stiletto. Now say won't hurt.

Tohsgib posted 02-09-2011 03:40 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
How this pertains to the F70 is this. If he bought a F60 or a F70(which we HAVE discussed) it would run the same prop because the redline is higher and that is all. The extra 10hp would push the 60's same prop higher up and give higher top speed. The cruise speed & RPM would be EXACTLY the same. So more hp on a modern 4 stroke does not mean slower rpm's at cruise, quieter operation, better economy, or longer life...PERIOD! On most E-Tec's it would do exactly what you state.
fishgutz posted 02-16-2011 02:21 PM ET (US)     Profile for fishgutz  Send Email to fishgutz     
First of all the F60 and F70 would NOT run the same prop as the gearing is different. The T60 and F70 share the same gear case.

Second the F70 has 4 valves per cylinder and the T60/F60 have 2 valves per cylinder. The whole power curve will be different in comparing the 2 motors. There is much more of a difference than just the different maximum recommended RPM.

Third, it isn't really "redline". It is the maximum recommended RPM range to achieve the specified horsepower. Most, if not all outboards will run above "your" redline. They just won't produce anymore horsepower and you're wasting fuel.

Fourth, If you look at the performance charts of same boats with the F70, F60 and T60 motors on Yamahas website you can see the difference. bulletin_4stroke_midthrustjetport_bss_sa9f1a.tmp.pdf
and bulletin_4stroke_highthrust_bss_sa9022.tmp.pdf
I know these performance charts can be somewhat inaccurate but these are essentially the same boats with roughly a 50-60 pound weigh difference running an F70 and a T60. They run different props to achieve the max recommended RPM. The cruise speeds are different as are all speeds at certain RPM.
If the boat with the F70 ran a 14 inch pitch prop like the other boat with the T60 then the max RPM would be well above the 6300 RPM max.

Peter posted 02-16-2011 07:28 PM ET (US)     Profile for Peter  Send Email to Peter     
You mean to tell us that if you have a higher HP 4-stroke motor on the transom that is a kissing cousin to a lower HP motor you can get the same cruise speed at a lower RPM? That's amazing! ;)

Seriously, I think the gap between the T60 and the F70 is closer than those reports show. The F70 boat is pushing less weight and is operating in more favorable atmospheric conditions.

fishgutz posted 02-16-2011 08:28 PM ET (US)     Profile for fishgutz  Send Email to fishgutz     
Peter, that is correct, because you will be using a steeper pitch prop.
Peter posted 02-16-2011 08:55 PM ET (US)     Profile for Peter  Send Email to Peter     
What if the motor is made by Suzuki instead of Yamaha? ;)
tedious posted 02-18-2011 02:44 PM ET (US)     Profile for tedious  Send Email to tedious     
Then we'd be getting FUD from SuzukiSlammers instead of YamaHaters.


Tohsgib posted 02-18-2011 04:02 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
If it was made by Suzuki and I posted my REAL WORLD data about 2 similar boats(smirked montauks) running both the 60 & 70 side by side with the same prop and same gear ratios and different redlines and posted the speeds...Peter would still argue that I was wrong and his couch potato "calculator" is correct so what frigging difference does it make what brand they are?

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