Moderated Discussion Areas
  ContinuousWave: Whaler Performance
  Reduced Weight In Four-Cycle 90-HP Outboard Engines

Post New Topic  Post Reply
search | FAQ | profile | register | author help

Author Topic:   Reduced Weight In Four-Cycle 90-HP Outboard Engines
87montauk posted 08-15-2011 04:09 PM ET (US)   Profile for 87montauk   Send Email to 87montauk  
When, if ever, will a 90-HO four-cycle outboard engine weigh less than 300-lbs? The Yamaha F70 is nice at 260-lbs but giving up 20-HP is hard to do. If one were to find and buy a Yamaha 90 TLR, in 20 years how available will Yamalube be?
Peter posted 08-15-2011 05:36 PM ET (US)     Profile for Peter  Send Email to Peter     
Not in my lifetime. Not in my kids' lifetime. The only way they get a 90 4-stroke under 300 lbs is through the use of exotic materials and if they did that, no one but the U.S. government would be able to afford one.

2-stroke oil will be around in 20 years. Yamaha still makes and sells conventional 2-stroke outboards, just not in the U.S. and Europe.

captbone posted 08-15-2011 05:49 PM ET (US)     Profile for captbone  Send Email to captbone     
I think that we will certainly see it and is certainly possible today.

The technology is already here. Look at the Yamaha SHO 4.2 liter 250hp outboard 20 inch shaft at 505lbs. They could easily adapt the plasma cylinder coating and get a 300lbs 115hp four stroke. The problem comes down to spending the money for R&D and retooling of the assembly line. If the economy was not in the tank, we would be able to see some big outboards (450hp) and also some light weight ones. It just does not make sense economically at this time.

Peter posted 08-15-2011 06:18 PM ET (US)     Profile for Peter  Send Email to Peter     
If they used all the tricks that they did going from the Yamaha F225 Sport to the SHO 4.2, they still would be over 300 lbs. At 505 lbs, the SHO is 86 percent of the weight of the F225 Sport (586 lbs). Assuming that a similar "new" Yamaha 90 would be 86 percent of the weight of the current Yamaha 90, the "new" Yamaha 90 would be tipping the scales at 317 lbs. Perhaps if they did not increase displacement they might be able to get the weight close to 300 lbs.

Until conventional bread and butter 2-strokes like the 60 to 90 HP models are banned througout the world, I don't see Yamaha making any significant weight reducing SHO like improvements to their mid-range 4-stroke line.

Russ 13 posted 08-15-2011 07:01 PM ET (US)     Profile for Russ 13  Send Email to Russ 13     
Does Yamaha still sell the conventional 2 strokes in Canada?? Aye?
pcrussell50 posted 08-15-2011 07:54 PM ET (US)     Profile for pcrussell50  Send Email to pcrussell50     
Here in the developed world, we have the luxury of paying for things (those that are willing, anyway), based on quietness and lack of smoke. In other parts of the world, performance cannot take a secondary role to aesthetics, or in military special ops, where troops might have to carry their propulsion device as if their lives depend on it.

Sometimes in life, "the game" must be played at a level that does not allow room for trifles.


captbone posted 08-15-2011 08:37 PM ET (US)     Profile for captbone  Send Email to captbone     
The existing 90hp four stroke that Yamaha has is a whale and poor example as a jumping off point.

If you started with a more modern design like the Suzuki 90hp (341lbs) they could easily get it under 300lbs if they tried using plasma bores and other weight reducing tactics used in the SHO. That is also not even scratching the surface of the technology that is currently available. Direct injected four stroke engines are currently being used in the automotive industry with great success and even more weight saving.

Weight has become less of an issue and focus point for engine manufacturers as repower is not the primary market and modern vessel are designed to handle heavier engines then in the past.

The technology is certain their, I just doubt the desire and market would make the investment worth the cost right now.

Tohsgib posted 08-16-2011 12:07 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Me winning the Lotto, when?
captbone posted 08-16-2011 12:46 AM ET (US)     Profile for captbone  Send Email to captbone     
It does not matter anyway catalytic converters on outboards in 2016 will add another 50lbs anyway.

Peter posted 08-16-2011 08:35 AM ET (US)     Profile for Peter  Send Email to Peter     
The question asked is not "Is an under 300 lb 90 HP 4-stroke possible" but rather "When will someone like the original poster be able to buy one because they are commercially available?"

In the last several years, both Suzuki and Honda launched their second generation 90 HP 4-stroke outboards. Both are significantly lighter than the 1st generation outboards but also lost some displacement, evidencing the fact that outboard weight on the transom DOES matter (the smaller the boat, the MORE it matters). They had plenty of opportunity to use sophisticated materials and engineering to get the weight down below 300 lbs, yet they did not come remotely close to that. Why? Cost.

In the case of Honda, many of their outboard powerheads are derivatives of their automotive engines. For example, the 90 HP powerhead is a derivative of the Honda Fit automotive engine. So unless Honda undertakes the use of more sophisticated materials and engineering, such as sleeveless, plasma coated aluminum cylinder bores in their automotive engines, you won't see it in an outboard powerhead. New outboard motor development depends highly on what goes on in their automotive engineering R&D.

Regarding catalytic converters in 2016, please point to the EPA regulations that will require such. Perhaps you know something that the EPA not announced in terms of rule making?

thegage posted 08-16-2011 09:29 AM ET (US)     Profile for thegage  Send Email to thegage     
Direct injected four stroke engines are currently being used in the automotive industry with great success and even more weight saving.

Certainly they can save weight, but they have enough issues not to be considered a total success. For instance, valve and injector tip carbon build up is very common and not easily addressed.

John K.

captbone posted 08-16-2011 12:12 PM ET (US)     Profile for captbone  Send Email to captbone     
After sitting back and re-reading you point Peter, I will change my tune and agree. I certainly think that they are possible even with todays technology but even according to my own words, I just dont think there is the motive to get the engines that light.

While I agree that weight certain does matter, I dont think it has that drastic effect on the bottom line of the manufacturers. New boat sales and OEM accounts for the vast majority of sales and these boats are designed for the weight. While a lighter OB will certainly result in more sales in the repower market, I dont feel that investing millions of dollars in development and R&D to increase sales in the 90hp repower market(an extra 500 units a year increase?) would make sense. An outboard motor manufacture would have to redesign the engine completely and I dont see that coming anytime soon.

We have been dealing with carbon build up on 2 stroke DFI engines for years and it has been a non-issue with todays tactics for combating carbon build up. A 4 stroke DFI would be an easy transition of boat owners. Automotive owners would balk at the idea of having to add quickclean or ringfree on a regular basis but to the boater, thats the cost of doing business.

While I dont have a specific EPA announcement to point to, 4 star emissions for outboard motors is coming and I feel it will be announced within the next year for a 2016 deadline.

Peter posted 08-16-2011 12:46 PM ET (US)     Profile for Peter  Send Email to Peter     
The EPA cannot simply make rules without going through the public notice and comment procedure. There is nothing that I can find where the EPA has posted proposed new rules via the public notice and comment process. In the last round of rules implemented in 2010, after public notice and comment, they acknowledged the difficulties including safety and reliability concerns with catalytic converters in outboard motors.

As fuel prices ever increase, boat makers will come under greater pressure to improve efficiency. Given that they have maximized what they can get out of a hull shape, the future more efficient boat is likely to be lighter and so outboard weight on the transom will become increasingly important.

Tohsgib posted 08-16-2011 12:46 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
A rotary engine would easily make a 150hp 300lbs but cost is the problem. Most 90-115hp are considered "entry level" engines. People go to the boat show and buy their $13,999 SeaRay that will either have a 130hp I/O or a 90-115hp Mercury on it. If the outboard costs $1500 more than the I/O they won't sell any. Again 50lbs is 3-4% or a spare battery in the biggie. Stuff a few more McDonalds down your kid's throat and make them sit up front.
captbone posted 08-16-2011 01:03 PM ET (US)     Profile for captbone  Send Email to captbone     
4 star emission and catalytic converters for outboards are coming.

number9 posted 08-16-2011 04:23 PM ET (US)     Profile for number9  Send Email to number9     
It could be done without doing anything out of the ordinary and have a comparable to now price.

Yamaha for example could easily design and build a new inline four cylinder series. It could fit displacement/weight wise nicely between the F75/90 and F50/60/70 with a 300lb. goal.

It's not that they can't, they just have no reason to do that when they already have a 90hp that sells reasonably well.

Peter posted 08-16-2011 08:38 PM ET (US)     Profile for Peter  Send Email to Peter .

Interesting article but says nothing about proposed new emissions rules to be implemented by 2016 by any regulatory body. My take away from the article is that catalytic converters in outboard motors is a long, long way from being ready for prime time, if ever. There are numerous expensive problems to solve before it ever becomes commercially viable.

"It could be done without doing anything out of the ordinary and have a comparable to now price....Yamaha for example could easily design and build a new inline four cylinder series. It could fit displacement/weight wise nicely between the F75/90 and F50/60/70 with a 300lb. goal."

So are you saying that they could make a 300 lb 1.3L 4-stroke 90? How do you get 90 HP out of it, spin it up to 7500 RPM? Where would the mid-range torque come from to make it competitive with Suzuki and Honda 90s at 1.5L and particularly the 2-stroke E-TEC at 1.3L? They certainly wouldn't put a supercharger on the 1L F70 block because we all know what supercharging does to outboard weight.

pcrussell50 posted 08-16-2011 10:39 PM ET (US)     Profile for pcrussell50  Send Email to pcrussell50     
Both BMW and Honda have made normally aspirated automotive engines that have exceeded 100bhp per liter. And yes, they did it by stratospheric rpm... 9000'ish.

I suppose it could be done with an outboard, too. You need a different ratio for the foot.


Peter posted 08-16-2011 11:24 PM ET (US)     Profile for Peter  Send Email to Peter     
If you have a variable gear box, like a car does, then reving to 9000 RPM is no problem. Outboards don't have such. Therein lies an enormous difference.
Tohsgib posted 08-17-2011 08:20 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Those SeaDoo & Yamaha Jet boats with 200+hp 4 stroke inboards spin like 9-10,000rpms.
Chuck Tribolet posted 08-17-2011 09:43 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Given that carbed two-strokes were in the low 300s, it's going
to be a long row to hoe to do a four-stroke in that range.

Me: e-Tec.


Tohsgib posted 08-17-2011 03:39 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
The Suzuki 90 is 21 lbs heavier than a 90 E-Tec. That is like 2.5gals of fluid. Add the oil to the resevoir and it gets even closer. Suzukis are weighed with oil & prop but I doubt DFI's are. The reason I know this is the early DF60/70 was quoted as 348lbs for the first few years. They were then made to show it as it sits on the transom which went to 359 with oil & prop.
jharrell posted 08-17-2011 07:44 PM ET (US)     Profile for jharrell    
This thread is similar in discussion to the one I started here:

I did the math there on a hypothetical Yamaha 90 based on the power/weight/displacement ratios of the F70.

Here's what I came up with:

The Yamaha 70 makes 1hp for every 14.28cc taking that same power/displacement ratio to 90hp yields a 1280cc engine.

Doing a power to weight ratio on the Yamaha 70 shows 3.67hp per pound which would yield 330lbs for a hypothetical 90hp.

The new F70 still uses steel sleeves, if they went with PI cylinders like their larger motors I believe 300lbs is within reach and at least matching or besting the Etec at 320lbs should be quite attainable.

Of course simple ratio's don't tell the whole story, but it is a good starting point.

Peter posted 08-17-2011 09:24 PM ET (US)     Profile for Peter  Send Email to Peter     
Yes, absolutely right. The ratios don't tell the whole story because there is much more to making a useable, competitive outboard motor than WOT HP. A 1280 cc 90 HP 4-stroke would have a weak power curve as compared to a 1.3L 90 HP 2-stroke like the E-TEC or a 1.5L 90 2-stroke like the Optimax. A couple of models of Yamaha 4-strokes with weak power curves were exposed a few years ago when compared to similar displacement 2-strokes so I doubt that Yamaha would be looking to reduce the displacement of any of their 4-stroke outboards. In fact, their most recent development went in the opposite direction, increasing displacement significantly. Yamaha's next move to cut some weight on the 90 is to go to the plasma hardend sleeveless cylinder design and some carbon fiber cowling material but that won't get the weight anywhere near the 300 lb mark that was the subject of the original query and those tweaks are expensive.

Nick -- Suzuki's advertised motor weight is with battery cable, but no oil or propeller. Suzuki 90 holds 4.2 quarts of oil. E-TEC 90 reservoir holds 3 quarts of oil. So the difference in operational weight is probably about 23 lbs. Weight's not bad for a 90 4-stroke but they gave up some displacement and performance relative to the old DF90 to get there. Hopefully when they reduced the weight and displacement, they reduced the price too.

Tohsgib posted 08-17-2011 10:49 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Show me the notice. I KNOW that the DF70 was 359 with prop & oil. The 338 was not.
Peter posted 08-17-2011 11:13 PM ET (US)     Profile for Peter  Send Email to Peter     
Just look at any of their brochures. They tell you what the weight includes. Everything is dry, no prop. The old DF60/70 weight is advertised at 357 lbs. I assume they use the same method for specifying weight on that model as they do for all other models. So 357 is a dry, no prop weight.
jharrell posted 08-17-2011 11:15 PM ET (US)     Profile for jharrell    

Yes I think we all know 2-strokes have better torque curves than 4-strokes, you make sure we all know that over and over.

But to say 14.28cc per HP will make an unusable outboard is also to say the current F70 is unusable. Do you really think that?

From all reports I have heard it a great motor, not as strong as other larger displacement 70's buts hard to beat the weight and fuel efficiency

Tohsgib posted 08-17-2011 11:19 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Wrong!!! 21 lbs is not a mistake on the old 1.3L Suzukis.
Peter posted 08-18-2011 07:41 AM ET (US)     Profile for Peter  Send Email to Peter     
jharrell -- Please go back and reread what I wrote. I didn't write anything about the F70.

By the way, the ratios which you base off the F70 don't seem to make a good starting point either. If we follow the ratios you propose to make a 150 HP motor, it would have 2.15 L of displacement and weigh 550 lbs. Think that's a useable, competitive outboard?

jharrell posted 08-18-2011 01:13 PM ET (US)     Profile for jharrell    
I'm sorry I thought you where implying 1280cc 90 4-stroke would not be competitive or usable? Did I miss interpret that?

Suzuki's 140 motor is 1.9L, Honda's 150 is 2.3L seem's like your 2.15L is right in the middle, so the ratio seems to work.

Their weight's are 410 and 478 respectively, this show's weight doesn't scale linearly with HP like displacement does. So my 330lbs 90 would probably end up being less even with steel sleeves.

Tohsgib posted 08-18-2011 01:31 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Suzuki's 140 is 2044cc, the 115 is 1950cc.

Post New Topic  Post Reply
Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.