2 stroke vs 4 stroke

Where can one find objective info on comparing the direct injection two strokes to 4 stroke outboards? There are lots of opinions out there, but has anyone done really objective data collection on this subject? What are actual maintenance and operating cost of the engines?

 

Can't give you any numbers , but how many hours do you think it will take to service 4 valves per cylinder on 6 cylinders?

Dealers are $75 an hour, and these are a bit complex for a backyard "mechanic".

FAST FRED

 

Yeah ,--- I would stick with a 2 stroke for the time being.

 

I talked to a local mechanic today - he said that the new HPDI two strokes do not hold up - his explaination was that they run so lean that they burn up. He recommends to stick with the EFI two strokes - good on gas milage and long lasting. Anyone have any comments on the HPDI vs EFI? How does the fuel consumption compare on these?

 

earlier this year i unbolted a yam F-100 4 stroke and replaced it with a merc 115 Opti. All other things being equal, i am now running a full 5-6 kts faster and i am getting .2nmpg better range. I am never going back to a 4 stroke.

For the same weight, why not opt for the extra HP?

 

1995 Montauk and 90 hp Yamaha

Hello,
This is my first post, and am not really sure what happens next. My situation is that I just bought a 1995 Montauk with 1995 direct oil injection 90 hp Yamaha 2 stroke. Boat was in Michigan and Florida with very little use when I bought it. Brought the boat to Birmingham and had local marine service go through from bow to stern. Alabama Marine pronounced the engine as being in great shape. My experience is with larger boats: diesel and I/O and am unfamiliar with outboards. The 2 stroke reminds me of a lawnmower [which I could never get to run], I listen to the "pop pop pop" and expect the thing to quit. I know that all this is me not understanding the engine. Where do I start to learn about these Yamaha outboards in order to enjoy it and keep it running? Am reading / listening about stuff like fuel additives for non-guming, "ring-free", etc. What are the traditional things that go wrong with these engines? Any help is greatly appreciated.

 

If you are running a 2 stroke I would mix the gas (and keep oil in the pump as well) regardless of what the manufacturer says. Those oil injected 2 strokes are injecting oil at the rate of 100 to 1, possibly more. You can mix up gas at 40 or 50 to 1 and still never foul a plug even if you are going slow all the time, which most people don't do. I have nothing but good things to say about Yamaha engines, I have a 1985 25 horse 2S that is still running great, as well as a 99 2S and an 03 4 stroke. Those new 4 strokes are great on gas, I wouldn't believe everything you hear. Loveofsea is the only person I have ever heard of who would choose a Mercury over a Yamaha, I have had nothing but bad from Merc. For people who want to stick to American made, Johnson all the way, they last forever.

 

Hello RAWRF~

i have less that 90 hours on this engine and i am running between 44:1 to 51:1 fuel/oil ratio. The varience is a function of the computer according to its demand parameters. The specs are a bit ambiguous. Reliablity is my biggest concern and i don't mind the expense of the oil consumption if it is going to protect that powerhead.

The Yam F-100 has a tiny lower unit and couldn't withstand the rigors of a SST prop. i was at an island 75nm from port when it gave out without warning @ 700 hours. (when i think about all the places that thing could have failed, i am humbled by the coinsidence of good fortune~

anyway, i sold the motor with a new L/U (150hrs) to a friend for a song.

So far i am very pleased with the Opti. For years i have cruised at 22-24kts, now when the seas are kindly, i run 28-30kts with better fuel economy than the yam @ 24kts.

For me, it is all about range; range broadens your options like nothing else...

 

Getting back to the original subject, objective data of 2S vs 4S, the only data I have ever seen is from Bombardier, so I don't know how objective it is since they own OMC. I personally wouldn't own an Evinrude E-Tec HPDI 2 stroke, too much to go wrong with all the electronics controlling everything, and I live nowhere near a dealer with a certified mechanic, tho I am sure the others with EFI are just as prone to problems in that regard.
Hello Loveofsea--what exactly did you change from stock when going to the SST prop? i.e. pitch and size? I know they are stainless so they are heavier, is that why the Yamaha LU went out? I don't want to make the same mistake, although I never run stainless anyway, would size tend to do that also? Is the small lower unit inherent in all Yamahas? I have never had a problem with mine and never gave a thought to the lower unit. Thanks

 

Hello rawrf

I never used an aluminum prop so i don't know how it would compare to the SST. I was told by the daler that sold me the lower unit that they don't handle the extra weight of the SST prop. He was a yam dealer and he said that every time you engage that heavy prop, it wears out the dogs just a little. The size of the prop probably won't hurt your L/U as much as the powerhead if it were grosely oversized. If you are running an aluminum prop i wouldn't worry about it.

i looked at the E-tecs and after having a problem with the voracity of the people at evinrude, i got my deposite back and went with the Merc. So far i am very pleased with that decision.

 

I use aluminum because I run exclusively on a river and hit bottom pretty regularly, and with a stainless prop you will wear out your lower unit with repeated small hits or, with a bad collision, break the clutch dogs, bend the prop shaft, and other things. Plus aluminum is cheaper.

 

RAWRF, you say:

Loveofsea is the only person I have ever heard of who would choose a Mercury over a Yamaha.

That may be true from your experience, but you also don't know anyone else who runs these seas like i do

If there is something you can tell me about Mercury or Yamaha that i am not aware of, i'd be all ears...



BTW, i've had two Yamahas and i dumped each one for a merc....the yams were the only two engines that ever failed me...never again...

 

Evinrude ETEC over 4 stroke for me.

It isn't mine but we looked at both and have a mate with an almost identical boat (5m) with a 4 stroke. We get very similar fuel economy but plane much faster. The 4 stroke I reckon is slightly quieter. (Different brands so that could also be the difference)

 

boy you opened a can of worms
this is the classic ford vs chevy argument everyone will say something in the end its up to you
have them both two stroke with 3000hr and four strokes with 3000hrs bottom line they both do the job and if you take care of them they take care of you
not going to say any names so find out what dealers are in your area and what there techs say if you find an honest tech he'll tell you there all good but this is what he works on

 

i work on harbor patrol boats using 150hp hondas,we switched from cummins diesels with outdrives and have found them to be nearly as fuel efficient as the diesels and much smoother and quieter.honda rates them as 10,000 hr motors and the coast guard locally rates them at 15,000. we've been extremely happy and put a minimum of 2500 hrs per season on them.