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Author Topic:   Repower 1987 25-Outrage Whaler Drive
davey posted 11-16-2001 07:56 PM ET (US)   Profile for davey   Send Email to davey  
I am original owner of 1987 25-Outrage powered by twin 150-HP Yamaha outboards counter rotating on a Whaler Drive. The time is coming to replace my engines having 1,500 hours. Dilemma is, do I replace with same 2-stoke package as purchase new in l987, or do I consider twin new Yamaha 4-stroke of equal or similar horsepower. Can anyone help me with advice as to which way to go???? Whaler tells me there are no weight restrictions on Whaler Drives, however suggested I be concerned about the width of the 225-HP 4-strokes. Actually, a step down in horsepower would be fine with me from [twin?] 225-HP, but perplexed about 2-stroke vs. 4-stroke. Can anyone be of help to me with my decision making process please?
Peter posted 11-16-2001 08:37 PM ET (US)     Profile for Peter  Send Email to Peter     
You would have to mount twin Yamaha 225 4s farther apart than your 150s. Several months ago I did a payback calculation between a single Yamaha 225 2s EFI and a Yamaha 225 4s on a 22 Revenge. My calculation led me to the rough conclusion that it takes approximately 300 running hours at cruising speed (30 mph) before the fuel savings on the 4 stroke paid for the price premium. Up here, 300 hours is about 6 seasons. Of course, the calculation depends on the price of gas which was 2.00/gallon at the time I did the calculation. If the price goes down, then the payback takes even longer.
JBCornwell posted 11-16-2001 11:01 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Oh Peter, Peter! You bean counters just seem to never learn to value intangibles!

What is the smooth, quiet operation and "drivability" of a 4 stroke worth?

What is the probably doubled life of a 4 stroke over a 2 stroke worth?

What is the probably halved maintenance and doubled reliability worth?

What is freedom from smoke and stink worth?

Did you include the cost of TC-W3 oil in your cost/payback analysis???

To a user of 4 strokes who suffered with 2 strokes (granted, not DFI) for 50 years the 2 vs 4 stroke issue is a genuine no-brainer.

Davey, DO NOT decide this until you have taken a day cruise on a 4 stroke equipped boat similar to your own. Even if it is only powered by 115s.

Red sky at night. . .
JB :)

Tom W Clark posted 11-17-2001 12:29 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Oh JB, JB! There's nothing wrong with a nice little warm and fuzzy cost-benefit analysis! Now, having said that, you are right about the need to factor in all the costs and all the benefits, whether easily quantifiable or not.

To address a few of your questions: Yes, Peter included the cost of TC-W3 oil in his analysis (if I remember that thread correctly).

Doubled life expectancy?! That remains to be seen and currently there is no reason to believe there's any.

Halved maintenance and doubled reliability?! Actually, four strokes require quite a bit more maintenance and: see above.

No brainier? Hmmm, I think it requires quite a bit of brain power to decide.

Peter, I'm not sure because davey's post is a little ambiguous, but I think he is considering a pair of motors totaling c.225 hp, not a pair of 225's. If he put a pair of Yamaha 115's, wouldn't he have enough room and be able to use the existing bolt holes?

I have heard very good things about the Yamaha 115 four stroke. Unlike most four stokes, it is quite snappy in its throttle response and apparently faster and more powerful than Yamaha's 115 two stroke. (an under rated motor?)

But I would love to see davey's boat with a pair of Yamaha 225 four strokes. (Yes, JB, it is rated for 450 hp) That would be my idea of the ultimate Outrage.

But really, if I were in davey's shoes I'd be a little cautious about repowering at all right now. We seem to be in a state of flux when it comes to outboard technology. Big four strokes are relatively new on the market and I hate buying things before all the bugs are worked out.

davey, can you milk another season or two out of your current power? It might pay in the long run.

David Ratusnik posted 11-17-2001 08:24 AM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
The Yamaha 200/225's are wider but not so with the Honda 200/225's. 4 stroke Honda's are quite sleek. David
jimh posted 11-17-2001 08:24 AM ET (US)     Profile for jimh  Send Email to jimh     
This is an interesting argument, and it happens to be one that is especially germane to Boston Whaler because they were the first boat company to manufacture and market 4-stroke outboard engines. I am referring, of course, to the Bearcat line of outboards. It is also interesting that Whaler promoted the Bearcat outboard with many of the same arguments made here; this was from 1966-1972, over thirty years ago.

I think it appropriate to review my article in the REFERENCE section on Bearcats, with special attention to the comments near the end of it on the marketing claims of cost savings through fuel econonmy. Gas was quite a bit cheaper then, but so were the engines.

See Bearcat History Article .

jimh posted 11-17-2001 08:45 AM ET (US)     Profile for jimh  Send Email to jimh     
To help focus this discussion, I think it appropriate to point out that davey is from California, a state which has imposed strict limits on outboard engine emissions. On the other hand, I wonder if a boat like his 25-Outrage is used much on inland lakes in California. Do state regulations promulgated by California affect boats on the ocean in its coastal waters?
jimh posted 11-17-2001 10:38 AM ET (US)     Profile for jimh  Send Email to jimh     
When making estimates of fuel savings that can be anticipated to acrue from conversion to more efficient engines, there are some pitfalls that should be avoided.

First, the differential in fuel consumption between conventional 2-stroke outboards and modern 4-stroke (or "low emission" 2-stroke) outboards will tend to be least in terms of percentage of difference at crankcase speeds near Wide Open Throttle (WOT). This is because conventional outboards are most efficient at that speed.

At lower speeds, the conventional 2-stroke will be, in terms of percentage difference, much less efficient than a modern engine. You might think, "That's great because I am going to be running the engine most of the time at speeds way below WOT."

The catch to this line of thinking is that the savings that acrue in terms of cost-per-hour of operation tend to decrease at lower speeds, too. Take this example:

Say an older engine burns one gallon per hour at trolling speed, while a modern engine burns only half as much. Wow, that modern engine is TWICE as efficient. That's a great savings. A 100% improvement in fuel consumption.

But we are only talking about saving a half of a gallon per hour of operation. If gas is $2/gallon, the modern engine saves only $1/hour over running the old engine.

If the price differential is on the order of one thousand dollars, then the savings don't begin to acrue until you are about one thousand hours into the more expensive engine. That might be over ten years for many recreational boaters.

What about the oil for the 2-stroke? OK, in a thousand hours of operation at 1-gallon/hour there will be a thousand gallons of gas burned. With a ratio of 100:1, that means we'd burn ten gallons of oil. If you use WALMART oil--which you can in an old style 2-stroke with no problem--you are talking about $60 worth of oil. Remember, that is $60 of oil over maybe ten seasons of use.

In that same 1,000 hours, you will have had to change the crankcase oil on your 4-stroke, change the filter, dispose of the old oil and filter properly, and haul your boat out of the water to accomplish all this. And you wil have had this expense at least ten times. I don't think that a rigorous analysis of the costs of all this maintenance (unique to the 4-stroke) is needed to see that it will cost more than $60 to accomplish it ten times. It will probably cost $60 to accomplish it EACH time!

Then there is the cost of the lost opportunity to use your boat while the 4-stroke engine is in the shop or the driveway and getting its crankcase oil changed.

Also, there is lost income from tying up the $1,000 in the new engine. Even investing in Savings Bonds, that $1,000 invested for ten years can yield considerable return. You can probably double it.

So ten years down the road, the 4-stroke engine is just about paid off its higher cost and now the savings can begin. The 2-stroke engine has a kitty (the original $1,000, plus interest) that you can now begin to withdraw from to buy the slightly more gas you'll need to continue to operate it.

We have also seen that many of the "modern" and "low emission" engines require special components and materials to maintain them. Instead of sparkplugs that cost $1.50, the newer engines need sparkplugs that cost $19.50! And instead of running a whole season on these plugs, they may need them replaced regularly to sustain good performance. Don't forget to subtract these costs from the gas savings that you'll begin to acrue after ten years.

The engines may also require special oils for lubrication, and in the case of the 2-stroke low emission engines, rather expensive sythentic oils are often specified to maintain them in proper condition. More costs of ownership for the "modern" engine.

All of the costs I have cited above are pretty much routine costs, so we have not yet looked at the costs of additional maintenance needed to keep the "modern" engine going strong. If you zap the engine control module (ECM) be prepared to spend ALL of the money you planned to save on gas in the next ten years to replace it.

And there are other exotic parts that can be anticipated to need repair. Things like high-pressure electric fuel pumps, injectors, solenoid operated valves, and so on, will all tend to make the more complex "modern" engine more prone to failure than the corresponding conventional 2-stroke.

In the specific case of the Honda 225-HP engine, there is the unbelieveable complexity of having two separate cams and valve trains which produce two separate sets of valve timing, changing with different engine speeds and selected by electrically operated solenoids. I am sure this is a masterpiece of engineering, but as a system it is vastly more complex than the reed valves on a 2-stroke and thus likely to be a source of greater expense to maintain over a ten year period.

bigz posted 11-17-2001 11:27 AM ET (US)     Profile for bigz    
While old JimH was doing his deep analysis and I was thinking a long simpler lines.

Davey are a few suggested thoughts to keep in mind --- for the $$ would strongly suggest sticking with 2 stroke Yam OX66 EFI's -- you have the rigging already and frankly as Peter (sorry JimH -- Peter basically spoke up first) mentioned economics don't justify the 4 stroke or the DFI at this juncture.

Oh the "ding dong" intangibles hell always buy a set of ear muffs if that pleasant growl of big two strokers upset your sensitivities. When running at cruising speeds everything equalizes out -- the wind noise on a cc boat is the real noise producer.

What in tarnation is "drivability" a Detroit marketing term transposed to outboards? Oops I degrees-- sorry --

Davey has gotten 14 years from the Yamaha's and would guess you'll be able to get similar from a set of new ones.

JB what say boyo about 14 years of dependable service which Davey has gotten from big engines which are usually pushed and pushed a lot harder than the baby stuff under 100 hp!!

Davey by the way we have a pair of 200hp '87 Yams with about 1200 hours and they are still running strong. A little smoky perhaps then again love to see a little oil burning up, then I know they are lubricating up ---

Under Davey's conditions only way to go is back to Yam's, this time the EFI's which he'll find awesome compared to his current ones and give him hopefully years of trouble free service just like the first pair.

davey posted 11-17-2001 03:19 PM ET (US)     Profile for davey  Send Email to davey     
to the many of you for your kind replies to my choice of 4 stroke vs 2 stoke, I appreciate all of your input so much. I use my rig in the Pacific, it is moored in the Santa Barbara Harbor, and after reading your expertise it appears as thou I should purchase new Yamaha 150's, two stroke, vs 4 stroke for all of the reasons stated. Thanks for your concern to all of you. Now, anyone have a good source for the purchase of new Yamaha 150's, two, counter rotating? I assume I can just purchase the motors and use my current guages, cables, tie bar, ss props etc etc, or do you suggest I replace any of these with the purchase of new 150's?????? thanks so much, I value your input as I dont have much expertise in this area.....davey
bigz posted 11-17-2001 04:00 PM ET (US)     Profile for bigz    
Check your control cables thoroughly, at 14 years just might want to replace them. I guess you have the 704 dual Yam controller if it is still smooth just lubricate it and attach the new cables.

I heard the new Yam LCD digital gauges were really nice but pricey -- if your tachs are reading correctly wouldn't bother --- over time if needed can always swap out gauges with newer ones. Your oil tanks should be fine (new ones aren't cheap). Oh, Yam offers some nice rigging cable tubing and connectors these would be nice to have a clean look on the Whale drive ---

Davey for you information a set of 200 hp is only going to run a little more -- the 150 and the 200 share the same head yeah know.

Good luck Z

lhg posted 11-17-2001 06:13 PM ET (US)     Profile for lhg    
As an owner of a twin engine, full transom 25 Outrage, I agree with BigZ wholeheartedly.
(although, BigZ, as a Ficht owner I am surprised to see you recommending EFI's!! What are you telling us?)

I have put myself in Davey's postion many times, trying to figure out what I would purchase if new engines became needed at this time. Fortunately, not necessary.

But for large V-6 engines, the outboard world seems to be in a bit of turmoil. And for this reason, I agree that I take the simple approach like BigZ, rather than all "payback" calculations. For me, the most meaningful "payback" is initial lower cost invested (EFI 2 strokes, Merc or Yam being only makers) and on-water reliability. In both of these categories, the EFI's win hands down, with an advantage to Mercury's lower initial purchase price, quieter running, and greater HP output (speed). The Merc's will smoke more on start up, however, because of their oil injection design.

For Davey's Whaler Drive 25, I STRONGLY recommend moving up to 200's. Weight is the same, and the WD model needs the extra HP.
Forget a conversion to a big single, on a boat used in the Pacific. Nor would I recommend anything less than 150HP twins.

What is the current picture on big outboards?

1. 4 strokes - I'm sure they're probably pretty good, although I hear power output at certain rpm ranges is not as good as the 2 strokes. But they are pricey, heavy and not yet proven. I don't want to be Yamaha, Merc's or Honda's test subject. A pair of these things will weigh 300-400lbs more than a pair of EFI's. That's a lot! (Merc 200 EFI's weigh 410 lbs each)

2. the DFI's. As great as their potential may be, the current Optimax & Ficht problems just aren't worth the risk (of lost boating time & offshore confidence) right now, nor worth the additional cost, weight & frequent high priced spark plug changes. I know less about the Yamaha DFI's. These engines are also much louder to run than the conventional EFI's from my experiences. But if one must buy one of these, I hear the Merc 135's and 150's (basically same engine) have the best track record so far.

3. What does all this leave? The tried and proven big two strokes, and only two real makers, Merc and Yamaha. Bombardier will probably not be much of a force in this limited time frame market, being forced to concetrate on the Fichts. Besides they have no fuel injection technology. The carbed engines are the cheaperst, but as Bigz says, I would spend the $1500 extra (for the pair) on the EFI's. Easy starting, great throttle response and trouble free fuel delivery operation.

I think this smooth idle and low RPM smoke issue is overblown, and being used as a sales promtion item. Frankly, I like the sound of a pair of big strokes idling. But more importantly, if an engine is used properly, it doens't spend much time idling at 600RPM. Smoke on start up at the dock/ramp is obnoxious, we all admit, and one should not sit at a marina with idling 2 strokes, ala Cigarette boat syle. But once away from the slip, I ALWAYS shut down one engine, (don't need 400HP to go 5 mph) and bring the rpms on the running engine up to 1200 rpms for the no-wake trip out of the harbor or up the ICW, or just slow speed on the water enjoyment. The engine makes no smoke at this speed, and runs smoothly. Underway at planing speed, of course, the two stroke is barely any different than a 4 stroke. Trolling, incidentally, I also only run one engine, and at 1200-1400rpms smokeless operation. So I still don't see the big deal about the 4 stroke quiet idle. My idea of good boating is to spend as little time as possible at 600rpm's. 3000-4000 is my preferred range, and it is smokeless, smooth and very quiet!

Peter posted 11-18-2001 11:34 AM ET (US)     Profile for Peter  Send Email to Peter     
JB, JB, JB.....

No need to jump to conclusions here. My post was intended merely to present some facts for davey's consideration when making a decision. It did not advocate 2 stroke over 4 stroke or vice versa, however, for me personally, I couldn't justify the significant up front expenditure. If he were to repower now with 150s, it seems that his choices would not include 4 strokes. But if V6 4 strokes were available, the analysis would be the same. In 2006, the analysis is likely to be different as carburated and EFI 2 strokes are unlikely to be available.

Regarding the intangibles, I think Tom Clark has the issues pretty well covered. Personally, I actually like to hear my engine while I'm underway. In fact I usually fine tune engine speed by the way it sounds most of the time. Besides, as Bigz points out, wind noise at cruising speed is louder than the engine noise.

The big picture in the 4 stroke verus 2 stroke debate should probably require consideration of the additional manufacturing and disposal costs associated with the extra moving parts of a 4 stroke. I recall that some time ago Jimh posted a very thoughtful discussion on this part of the debate.

Bigz's suggestion to go up to 200 is a good one except that if counter rotation is important then I'm not sure that Yamaha offers counter rotation on the 200 EFI. Yamaha's web site seems to suggest that the smallest counter rotating EFI offered is the 225. You can get 150 and 200 HPDI's in counter rotating models.

Tom, I agree that a pair of F115's would probably fit side by side in the existing holes. I'm just not sure that's enough power for a 25 Outrage with Whaler Drive. However, I'm from the max horsepower school. My simple theory is that the larger displacement engine will have an easier time producing the same horsepower throughout the operating range of the lower horsepower, smaller displacement engine, and therefore, the larger engine will last longer. For example, a 150 running at WOT to produce 150hp will not last as long as a 225 running at 2/3's throttle to produce 150 hp.
Now, this begs the asking of a similar question: is it worth the extra dollars for the larger displacment engine(s) even though the operator is not really looking for increased speed?

bigz posted 11-18-2001 01:47 PM ET (US)     Profile for bigz    
Dog gone Peter, appears the Yam 150/200 EFI for 2002 models may not be available in CR.

I know for a fact the 2001's were available in CR. If this is fact, and Davey is interested. I would suggest he starts hustling up some west coast Yamaha dealers and see if he can't cut a deal on a pair of 2001's.

John from Madison CT posted 11-18-2001 02:29 PM ET (US)     Profile for John from Madison CT  Send Email to John from Madison CT     
If it was me, it would be simple, I would go with the Yamaha 200hp HPDI's. These motors are proving themselves to be very reliable and fantastically fuel efficient.

Yamaha's Web site has a Performance section that shows how the motors run on various configurations (different hulls).

They are available in counter rotating.

The newest Yammie 4 strokes are really getting some complaints as to their "punch". 2 Stroke fans are using this as the reason not yet to make the jump to this technology. They are also very big in circumference and may not fit together using existing holes on your bracket. Unless you can wait a year or 2 to see how these hold up, I would go with the HPDI's.

Good Luck,


bigz posted 11-18-2001 04:24 PM ET (US)     Profile for bigz    
Yam didn't make a big issue when they notified dealers this summer there were some problems with the HPDI bigger engines, in fact the rep sort of said cool it a bit on sales until we get these bugs ironed out. Guess they got them ironed out!

"Punch" is a relative term -- when your running dual 200hp+ engines a couple of seconds ain't making a big difference --- what you want is dependability more than a fast get away don't yeah know!

Your also going pay for a set of HPDI 200 hp about $3000 more than a set of EFI's! That ain't chicken feed, going to take a lot of oil and gas to re-coop that amount --

John from CT don't yeah just love to hear about motors like the Yam big 4 stroke on the market for all of 3 months and the HPDI's on the market for just over a year --- wonder how much of the talk is from actual use and how much is just plain old BS! Z

John from Madison CT posted 11-18-2001 05:48 PM ET (US)     Profile for John from Madison CT  Send Email to John from Madison CT     

Your correct, alot of what we hear is probably hype.
From my own long term experience however, I've become a big Yamaha fan. Especially in light of the clear and obvious problems with the Fichts and the Optimax's.

Maybe Yamaha wins by default ?


SSCH posted 11-18-2001 08:52 PM ET (US)     Profile for SSCH  Send Email to SSCH     
I own a pair of CR 200 HPDI Yamaha's (on my 25 Guardian). They are quiet, and so far (about 200 hours) very reliable. Fuel economy seems great. My last boat (22 Outrage) had a 200 carb Yamaha. These new engines burn 30% less fuel at 3500 RPM than did that motor. Of , now,there are two of them and the boat is a very different load. I get about 2.1 mpg at 3500RPM in the Guardian.

If I had to bet, I'd bet the HPDI is quieter than the EFI.

I've heard that there is a head gasket problem (maybe) with the HPDI engines in high hour engines. I hope that turns out to be a limited issue. In any event, I 've owned a number of Yamaha engines and have no doubts the they will stand behind their product.

jimh posted 11-19-2001 09:21 AM ET (US)     Profile for jimh  Send Email to jimh     
I am enjoying this thread; it is fun to discuss the vicarious spending of $20,000 on engines!

Although the "modern" engine offers better fuel economy, you should remember that this is not the motivation behind all that extra plumbing under the hood, all those extra valves and camshafts, or all the extra high-pressure pumps and injectors inside the shroud.

What is the real motivation behind the "modern" engine? What are they aiming for? The target is not better horsepower. The target is not better starting. The target is not better fuel economy. The target is not smoother running.

The target is low emissions that meet the EPA standard imposed on the outboard industry. And it is not an optional target. You have to meet the target or get out of the manufacture of outboards for sale in the US.

We have seen in automotive engineering that over a 25-year period the engines were able to evolve so as to meet the requirements of the EPA for low emissions, the quotas of CAFE for improved fuel economy, the demands of owners for good driveability, and to actually improve the engine lifespan, reduce its maintenance, and increase its reliability.

However, this did not all happen in the first year or two of development. Anyone who drove a car in the mid-1970's recalls how the additional of "emission controls" did not make for better engines.

The marine engine industry can stand on the shoulders of the automotive engine designers and jump over 20 years of development, but I think they still may have a few kinks to work out in some of their designs.

Jurisproodenz posted 11-19-2001 09:46 AM ET (US)     Profile for Jurisproodenz  Send Email to Jurisproodenz     
I certainly can't improve on the analysis here ... but ... let me add my 2 cents. Buy yourself a pair of 200 hp counter-rotating EFIs. Pocket the money. Enjoy the boat in confidence. If you can't get the Yammies, then hunt down the Mercs.

But certainly go for more power.

george nagy posted 11-19-2001 12:54 PM ET (US)     Profile for george nagy  Send Email to george nagy     
I'm in the same boat as davey, Well actually I'm in an 18' outrage but its the same year. I'm torn between suzuki's df140 weighing in under420 pounds and a new johnson 150 weighing in around 380 pounds.

LHG you forgot suzuki has had EFI for a long time they currently offer a 150 and a 225 2 stroke.

The initial cost you say, well in my case the 150 johnson is around $8k and the suzuki is also around $8k.

The warranty on two strokes are no more than 2 years and the warranty on 4-strokes start at 3 years industry wide.

If I had a 25' outrage I might not be considering a suzuki 4 stroke 140 I would be considering 2. (not sure about wd though)

davey,suzuki made 140 horses out of thier 4 cyl. 115 I bet next year yamaha does the same. You might want to wait.

I think this subject is too complex to be decided on so quickly, or maybe I just over analize things.

davey posted 11-19-2001 06:53 PM ET (US)     Profile for davey  Send Email to davey     
Again I thank you all for your valued imput. You have helped me tremendously, and largely because of your help, I am now searching for a pair of year 2001 Yamaha twin 200HP Counter Rotating 25inch Shaft Saltwater Series II OX66 or pair of Yamaha's HDPI year 2002 200HP Saltwater counter rotating....(I need to check and see what other changeouts I might be concerned with regarding my current binnacle mount controls, oil reservoirs, cables, ss props, etc etc vs the new engines I wind up buying.) If anyone knows of a good source whereby to purchase these engines and/or accessories, would be grateful to hear from you. I have been told that if I can find 2001 model year, there might be significant close out prices available??????
I wish I could be as informative to others as you have all been with me, certainly if I see a way whereby I can be helpful, not technically but rather thru experience factors, I will be happy to share my experiences with whomever I might be able to help! Now the search begins for the product....and the ensuing so costly. davey
bigz posted 11-20-2001 05:26 AM ET (US)     Profile for bigz    
Davey, suggest you either visit or call a few local Yamaha dealers (a visit might be best) and have them check Yamaha's current inventory for left over-s either EFI or HPDI.
This will give you the information up front whether you have to search dealers or just have a dealer you can cut the best deal with order them.

Note if Yam distribution has a pair in stock I would hang tough with any dealer for a substantial discount. Your holding the Ace, since the dealer would have them pre-sold up front and certainly could take a lower margin than on an engine/s he might have to inventory. I also know as of July Yam was already offering specials to dealers on both 2000 and 2001 left over stock.

Not sure on the HPDI engines but the EFI, as I mentioned above, all your rigging components on the current motors could be used. Again the control cables might have to be replaced and would also make sure your hydraulic steering is operating properly so that when the new units are rigged anything not right can be handled then.

Good luck, Z

Taylor posted 11-20-2001 05:14 PM ET (US)     Profile for Taylor  Send Email to Taylor     
Point of information... I had to look up some things in order to follow this very interesting thread. While the posters donít need this, some of the readers might want to know about:

Oil Injection - Oil is shot into the cylinder or the throttle body rather than drawn in with the fuel. Oil also may be injected at other critical points.

EFI - Electronic Fuel Injection - Fuel is spayed into the cylinder rather than drawn through a carburetor. Fuel amounts metered electronically.

DFI - Direct Fuel Injection - a 2 stroke technology where the fuel *and* air are sprayed into the top of the cylinder after the exhaust port is covered. Supposed to be cleaner than carbureted two stroke, reducing oil consumption by 50%

Optimax - Mercury's DFI system, licensed from an Australian company, Optimax.

Fitch - OMC's DFI system, Fitch Ram Injection, developed by a German firm.

HPDI - High Pressure Direct Injection. Yamaha's DFI system, introduced in 2000.

Here is a description I found at that was interesting.

Performance of the three systems is remarkably similar, but technically they differ. The Ficht system employs an electronic solenoid injector on each cylinder, controlled by an electronic control unit (ECU) that synthesizes information from 11 different sensors on the engine to determine the correct amount and timing of fuel injected, and ignition timing. An engine driven pump moves fuel from the tank to the engine, an electric pump sends it to the injectors at 25 psi and the injectors force it into the combustion chamber at 250 psi. A throttle body controls the airflow to the cylinder and an oil injector behind the throttle body mixes lube oil with the air being sucked into the crankcase.

The OptiMax system is similar but uses two sequential injectors per cylinder, one to pre-mix gas and pressurized air and the other to inject the mixture into the cylinder at 90 psi. A belt-driven pump pressurizes the air. An oil pump sprays oil directly onto the connecting rods. The ECU and injection system are standard automotive units.

Yamaha's HPDI employs two fuel pumps to bring fuel to the high-pressure pump, which sends it to the injectors at 700 psi. The ECU makes adjustments based on input from eight engine sensors. Yamaha's ignition system uses conventional spark plugs, as opposed to specialized plugs developed specifically for the other two engines. Ficht and Optimax plugs are pricey, $12-$25 each.

(hope all this formatting works!)

Finally, be aware that there has been a lot of heated discussion about the reliability of some Optimax and Fitch engines, in certain sizes and years.

And a disclaimer - I know something about engines, but not much about outboards. So I could be wrong here.

dgp posted 11-20-2001 06:52 PM ET (US)     Profile for dgp  Send Email to dgp     
Actually the Mercury OptiMax system utilises the Orbital Combustion Process developed by Orbital Engineering
jimh posted 11-23-2001 10:58 PM ET (US)     Profile for jimh  Send Email to jimh     
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