Difference between 4 stroke and 2 Stroke Outboards

[Beamishken]

That 5 hp yam you have is probably one of the best tender engines you will ever find, light ultra reliable &requires minimal servicing
Replace it at your peril cos you'll not be able to buy another new one
I'd be huffed if someone offered me a swap for my 5 hp yam 2/ for a new 4/
We have had ours for 8 years & it has been chucked in a locker in our boat never touched out of season never had a service or impeller , only ever had the carb cleaned once & one new plug it starts first pull & gets run ragged by the kids & never misses a beat
I'd bet if you treat a new 4 stroke like that it wouldn't last 5 mins
might be a different story if it was the main engine on a small yacht but for a tender it's a no brainer 2/ every time

 

[VicS]

That 5 hp yam you have is probably one of the best tender engines you will ever find, light ultra reliable &requires minimal servicing
Replace it at your peril cos you'll not be able to buy another new one
I'd be huffed if someone offered me a swap for my 5 hp yam 2/ for a new 4/
We have had ours for 8 years & it has been chucked in a locker in our boat never touched out of season never had a service or impeller , only ever had the carb cleaned once & one new plug it starts first pull & gets run ragged by the kids & never misses a beat
I'd bet if you treat a new 4 stroke like that it wouldn't last 5 mins
might be a different story if it was the main engine on a small yacht but for a tender it's a no brainer 2/ every time[/QUOTE

If you take a few moments to read the OP you will find that it is the main engine

 

[James W]

If you take a few moments to read the OP you will find that it is the main engine

Vic's right, it will be the main engine.

I think I might have a solution though. I'm going to go through the Yam 2 stroke with a fine tooth comb, clean it right up and make sure it's running as sweetly as possible, but I have also been offered a more modern 4 stroke Yamaha for a very reasonable price, serviced and guaranteed. I'll use them both and see which works best for me and the family.

As always though, i've learnt a lot from all the replies, thanks loads to all.

 

[GrahamM376]

If you do change, the Yam 2/ will certainly fetch decent money, shouldn't be any shortage of buyers.

 

[dartmoor]

In cold weather - two stroke every time. Four strokes are fussier starters and need more time on choke. Two strokes come off choke quickly, rarely falter, and just get straight on with the job.

Never convinced by the noise comparison. They sound different, both at idle and on full throttle. Personally find a small four stroke nicer on idle, but more unpleasant on higher throttle than a two stroke.

 

[Iliade]

Is oil in the sump still a problem. I thought that 4stroke had to be kept upright or the oil goes where it is not required. So you cannot just throw it on the deck as you deflate your dingy on a bouncy morning. Or just drop in the bot of the car.

Is there a solution to this problem. I am a bit lot to learn new habits!

My fairly recent Yamaha 4hp 4T can be lain on any side so long as the leg remains below the powerhead.

 

[Beamishken]

That 5 hp yam you have is probably one of the best tender engines you
might be a different story if it was the main engine on a small yacht but for a tender it's a no brainer 2/ every time[/QUOTE

If you take a few moments to read the OP you will find that it is the main engine

FYI I did read the ops first post but as my experience of the engine is as a tender engine I gave him the benefit of my experience with the caviat that that experience was as a tender engine
my post was intended to help the op not just try to pick up other peoples posts
perhaps if you have nothing helpful to say you'd be better off saying nothing in future

 

[VicS]

FYI I did read the ops first post but as my experience of the engine is as a tender engine I gave him the benefit of my experience with the caviat that that experience was as a tender engine
my post was intended to help the op not just try to pick up other peoples posts
perhaps if you have nothing helpful to say you'd be better off saying nothing in future

Didnt read my earlier reply either then!

 

[Beamishken]

Didnt read my earlier reply either then!

I read the entire thread & your earlier posts were valid but picking up on others posts adds nothing to the discussion

but if you want to feel superior that's fine!

 

[James W]

Guys, you've all been really helpful, thanks!

 

[VicS]

I read the entire thread & your earlier posts were valid but picking up on others posts adds nothing to the discussion

but if you want to feel superior that's fine!

You said "might be a different story if it was the main engine on a small yacht"
Read more at http://www.ybw.com/forums/showthrea...ke-and-2-Stroke-Outboards#g8LpRzqMUp6lpIJJ.99

Just pointed out that in the OP it was stated that it was the main engine ! Threfore it is as you say, a differnt story.

 

[Seajet]

That depends a lot on where it is mounted.

My 4HP 2 stroke hangs off the transom. And yes it's noisy and I prefer to be sailing.

BUT I was on a friends boat last year with a 4 stroke in a well in the cockpit. Boy was that noisy by comparison with mine, I would hate to have that configuration.

Must have been a strange well, I don't get any more noise ( or smoke ) from my 2-stroke than one would expect, and have the engine to hand so that I and my tools don't hang over the water to get at it, the prop in front of the rudder, weight in a much better place, prop staying immersed in waves and I don't have to face aft to adjust throttle or gears.

I'm afraid I feel the same way about transom hung engines, they always seem like the mark of a lazy designer to me !

As for picking up on other posts, VicS I don't believe I generalised or exaggerated...maybe if you have something to say about my comments you would be good enough to say it to my face rather than behind my back to someone else.

 

[Boltrope]

2 stroke every time. So much lighter and easier to service. An absolute pain when a 4 stroke dumps its oil, and that includes when they're put the right way up. They are harder to start than 2 strokes, sometimes being nasty and biting you back, snatching the cord. My 10hp 80's vintage 2 stroke runs quietly and smoothly and has a lovely power curve. But, for cruising engine the fuel consumption is an issue.

+1
Bought a new Yamaha F2.5 four stroke o/b in 2007. It weighed 20kgs and never, ever started first time. It was a pain to lug off the rail and onto the dinghy transom too.
Yes, it was quiet, but it was also very slow.
Traded it in for a 1990 Mariner 3.3 two stroke (completely rebuilt with all new internals) in 2013.
Not only is the little Mariner much lighter (13kgs) but it's 30% more powerful and it gets the 2.4m dinghy up on the plane when solo! Fuel mixing is not an issue (I use the measuring cap from a laundry detergent bottle - perfect for measuring out the right amount of oil for a five litre can of fuel.)
Yes it's noisier, but SO much lighter, more powerful, easier to maintain and of course that lovely smell that still reminds me of my old Yamaha RD250LC motorcycle

 

[Hadenough]

I've not read the whole trail because it's Friday and I'm chilled. Anyway, after ages of agony I replaced our beloved but aging, very powerful, light, 10hp Tohatsu 2 stroke with a 9.9 Mariner 4 stroke. Heavier, and less grunt (that's probably a good thing safety wise anyway!) but and a very big but - it uses 25% of the fuel of the old 2 stroke and no pi$$ing about with oil! We livaboard and use the tender every day so that has made a huge contribution to the cruising fund.

 

[dylanwinter]

I've not read the whole trail because it's Friday and I'm chilled. Anyway, after ages of agony I replaced our beloved but aging, very powerful, light, 10hp Tohatsu 2 stroke with a 9.9 Mariner 4 stroke. Heavier, and less grunt (that's probably a good thing safety wise anyway!) but and a very big but - it uses 25% of the fuel of the old 2 stroke and no pi$$ing about with oil! We livaboard and use the tender every day so that has made a huge contribution to the cruising fund.

I would never go back to two stroke

thirsty polluting spawn of the devil

 

[Iliade]

Guys, you've all been really helpful, thanks!

Now, about your anchor...

 

[James W]

Now, about your anchor...

Well, I can't work out which works best with a fin or twin keel.....

 

[Lakesailor]

Is it true to say that a modern 4 stroke 4hp with a high thrust prop would be as powerful as a 5hp 2 stroke?

Thanks!

Don't get hung upon maximum power figures. How often are you running at WOT (wide open throttle)?
4 strokes have more torque (grunt at low revs)

Is oil in the sump still a problem. I thought that 4stroke had to be kept upright or the oil goes where it is not required. So you cannot just throw it on the deck as you deflate your dingy on a bouncy morning. Or just drop in the bot of the car.

Is there a solution to this problem. I am a bit lot to learn new habits!

4 strokes normally need to be laid on one side. Which is marked on the motor. if you have trouble remembering just stick a coloured dot on the side of the cover that should be uppermost. It only takes a moment to spot that and lay the motor down accordingly. It's not the great problem people make it to be.

That depends a lot on where it is mounted.

My 4HP 2 stroke hangs off the transom. And yes it's noisy and I prefer to be sailing.

BUT I was on a friends boat last year with a 4 stroke in a well in the cockpit. Boy was that noisy by comparison with mine, I would hate to have that configuration.

Not an equal comparison. You need to try a 2 stroke in the well.

2 stroke every time. So much lighter and easier to service. An absolute pain when a 4 stroke dumps its oil, and that includes when they're put the right way up. They are harder to start than 2 strokes, sometimes being nasty and biting you back, snatching the cord. My 10hp 80's vintage 2 stroke runs quietly and smoothly and has a lovely power curve. But, for cruising engine the fuel consumption is an issue.

4 strokes need a different starting technique. 2 strokes need to be pulled over quickly and snatching at the cord is usually the way people do that. 4 strokes need a long, steady, pull. Getting the motor to just before a compression before letting the cord back in, and then using a long steady pull will avoid kickbacks.
My 4 strokes have normally started with just a gentle, hardly noticeable, pull.

I've had five 4 strokes and four 2 strokes. I would prefer the 4 strokes every time. (Didn't like the Honda though)

 

[Seajet]

I would never go back to two stroke

thirsty polluting spawn of the devil

Sometimes there is no choice Dylan, my 100:1 Mariner creates very little polltion, I suspect you still think of seagulls engines.

4-strokes are just too heavy to lift regularly, also a pain to stow as they're such prima donna's about their lube oil going into the combustion chamber.

My grand plan is to hold out with 2-stroke, then as soon as technology and my wallet reach an agreement it will be electic power for me, I tried hard to get this when we were going to build new Andersons but it's not currently ( pardon the pun ) viable for this sort of boat, would work on a moulded long keeler with batteries as ballast like a submarine, but the cost would be something else.

 

[dylanwinter]

It is not just the oil that is more polluting - the mix ratio is only part of it - the incomplete burn with two strokes is the problem

that "excess" fuel gets shoved into your lovely clean Chichester harbour - and if that is okay with you then so be it

D