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post #1 of 24 Old 11-27-2009 Thread Starter
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4 vs 2 cycle outboard

I always thought the 4 cycle was the gold standard outboard and the only issue was the price. I just talked to a ""old salt" who's opinion I respect who said he prefers the 2 cycle as he believes they are much more reliable. He said the 4 cycle is very fussy about its fuel and stalls and refuses to run due to fuel problems more often than the 2 cycle.

So he prefers the more reliable 2 cycle.
Is this true?
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post #2 of 24 Old 11-27-2009
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I Love my 4 cycle no more mixing gas and oil. My 2 stroke wasn't very reliable but it was also 30 yrs. old. The 4 cycles seem to run cleaner also.
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post #3 of 24 Old 11-27-2009
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In many ways, yes. The 4-stroke is heavier, idles quieter, produces much less emissions (why EPA loves it). The low-speed idle jets are teensy tiny pinholes, which is why they clog more readily than a 2-stroke. If you're in the land of ethanol fuel, the problems are magnified. I had one mechanic tell me that the only "cure" was to go for a fuel-injected engine, and to change ALL rubber parts, including the fuel lines, regularly. (Read: $$)

If we had it to do over again, I'd look very hard at a 2-stroke, although unfortunately they are being phased out in the US, may make parts/repairs a problem in future.
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post #4 of 24 Old 11-27-2009
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For cruising the 2 stroke is the way to go in my opinion. I never tow my dink so the engine comes off and gets stored on board. The incredible extra weight of the 4 stroke is not worth the benefits of the 4 stroke. Hopefully the 4 stroke will come down in weight in time.
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post #5 of 24 Old 11-27-2009
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2 Or 4 stroke motors equal out in emissions in the larger sizes in fact the 2 stroke E-Tec from Evinrude is among the cleanest BUT its only been taken down to 25 HP due to cost and the weight is about the same as a 4 stroke.

My Tohatsu 2 stroke is the model of reliability and the biggest issue with the 4 stroke is the carbs require draining if there sitting more than two weeks which is a PITA so many people run them dry which is about 1/2 empty and makes things worse

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post #6 of 24 Old 11-27-2009
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I've owned both and from an emissions and cleanliness standpoint, 4-stroke is the way to go. The fuel problems can be overcome by either draining the fuel system, running it regularly, and adding Seafoam.

The fuel stabilizer "Sta-bil" seems to react badly with ethanol blended fuel, sometimes creating a jelly or sludge after sitting for long periods. Seafoam fuel additive works much better in my experience with ethanol blended fuel.
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post #7 of 24 Old 11-27-2009
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For what it's worth, here's what I think:

The only advantages of 4 stroke engines are fuel economy and silent and cleaner running.

Next come the disadvantages:

They are a lot heavier (at least 50%) for a given power rating . This can be a problem in boats with a non centered engine mount bracket.

Their cost almost doubles that of a similar two stroke

They require more expensive and extensive maintenance more oftenly: Timing belts, valve adjustments, oil changes, the works... A two stoke only requires a spark plug every once in a while, gear oil every 100 hours and little else.

They are mathematically much more prone to failure, courtesy of the array of moving parts they need to run and that are, each and every one, subject to failure. A two stroke has essentially two moving parts: A crank, a piston and a connecting rod. No valves, no camshaft, no oil pump, no springs, no rockers, no timing belts, no tensioners...

This said, and presuming that no one intends to motor-sail across the Atlantic with an outboard, I find it very difficult to understand why to use a 4 stroke just to save a couple os bucks in petrol, since that seem to be the only game where they innequivocally win...

My trimaran has a Tohatsu 5hp, two stroke single cylinder outboard which lives all year round in sun and rain hanging on his bracket and has never missed a beat. He burns quite a bit of petrol if compared with a similar sized 4stroke (2,5L/h at full throtlle), thus being comparatively a bit more expensive per mile, but it is much lighter, simpler to operate and run and cheaper to maintain and has a much better weight to power ratio. In four years it has only cost me a spark plug, 1/2L of 80W90 gear oil and an anode... I guess that for the miles I intend to be motoring the extra expense on fuel doesn't bother me at all...

Furthermore on this subject, even the fishermen are returning to two strokes arround here. They got tired of changing oil and timing belts in their fancy Hondas and Yamahas and have returned to the good old carburettor two stroke Tohatsus and I don't ear them complaining.

Pedro

Portugal


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post #8 of 24 Old 11-27-2009
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If you're going cruising the two stroke is the only way to go. Simple, easy to troubleshoot and fix.

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Toronto in summer, Bahamas in winter.

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post #9 of 24 Old 11-27-2009
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One other point, not mentioned, is the four-stroke engines tend to be far less noisy. I'd also add that it simplifies inventory by not having to monitor two consumables, oil and gas, which would be the case for a two-stroke.

I've had a Tohatsu 4 stroke 3.5 HP and it is a very solid, reliable engine.

Sailingdog

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post #10 of 24 Old 11-27-2009
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We have 4s because we HAVE to NOT because we want to and IF your buying new in the US your buying a 4s


And there just getting warmed UP catalytic converters are coming in 2010 on in boards and they have diesels well in there plans

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Last edited by tommays; 11-27-2009 at 09:20 AM.
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