I've asked this question on other forums and got varying answers so I thought I would try here to see if there was anyone with THE answer. I have a Merc 115 4 stroke EFI. At startup, it smokes some, particularly when I leave it trimmed in. After startup it burns clean. I've been told that that is normal because when trimmed in, oil can seep into the combustion chamber. Mercury says its normal. Does this happen with any of you other 4 stroke owners? btw...it doesnt burn noticable amounts of oil and the crankcase is not overfilled. Any thoughts? Worry? or just go fish.

My 115 Honda has never smoked. I bought it after a 3 year horror involving a 90 HP Mercury 2 cycle that would never keep the carbs tuned and loved to explode lower untis.

Interesting. If Mercury says its normal, it seems to me like it is a design flaw. I still have some warranty on it so I will be taking it in at the end of the season and having them check it out, compression check etc. It's always done it, it runs great, it just smokes at startup.

Probably a little blow by past the rings when it's cold. If the motor gives good compression readings warm, it's not anything of concern.

Nearly all motors do it, (even hondas) but some disguise it better than others.

Are the cylinders on the Mercury vertical? How would oil seep in if you leave the motor trimmed?

I am no mechanic, but I believe cylinders are horizontal. spark plugs lined up top to bottom on back of engine.

My 4 stroke does not smoke.

mine don't either.

I would guess that a little trapped oil in the valvetrain is seeping past the valve seals. I personally wouldn't worry about it, but, then, I wouldn't buy a 4 stroke outboard. That's just personal preference, ok. I'm not trying to start a debate or argument. I like 2 stroke outboards. I've owned them for almost 40 years.

BUT, it seems to me like Mercury would have considered this issue in the engineering phase of the engine.

Artie

Pretty soon you will not have the option of not buying a 4 stroke. The EPA has begun to outlaw all 2 cycle motors, including boat motors, chain saws, etc... California has already done this.

Also, why wouldn't you buy a 4 stroke? No argument or debate, just curious.

Thanks Artie. Im curious also why you wouldn't buy a 4-stroke. I've had mine for three years now and have had no problems at all, the fuel economy seems great and it starts like a charm everytime. With the exception of my worry about the smoke at startup, I've been pleased. And the puff of smoke only bothers me if its a signal that Im gonna be in for trouble downstream. I'm going to take it in for a checkover after the season just to be sure.

Outboards are always under a load when they are running. A car engine rarely has the type of load that a boat engine has.

My 200 EFI has a crankshaft, 6 rods and 6 pistons. That's it. A 200 Yamaha 4 stroke has a crankshaft, 6 rods, 6 pistons, 2 cam chains, 2 cam chain tensioners, 4 cams, 24 valves....I think you get the picture. And what does it weigh? 575 lbs? My 200 EFI weighs less than 400#. 4 strokes will never match 2 strokes. They may make as much torque using superchargers and such, but that will add even more weight. Any technology you use to make a 4 stroke more comparable to a 2 stroke can be used to make the 2 stroke better.

And don't kid yourself about 2 strokes being outlawed. 20 years from now, there will still be plenty of 2 strokes running around. I don't care about what California is doing. As more and more people see what a social and economical sink hole California has become, it will lose alot of it's influence.

Personally, I always liked 2 stroke engines. They are light and they make lots of power and torque. I like the sound and the smell and the gobs of low end torque they make. And, yeah, I'm probably older than most of you. And I don't really like the idea that some appointed regulator makes some regulation and it becomes law without anyone voting on it. It circumvents the process. It's the only way special interest groups can get their way. I guess that's enough.

Artie

And mis informed consumers help fuel bad information.

CARB (california air resouce) just outlines emmissions, not where they came from. Two or four stroke, doesn't matter. The direct injected two strokes pass their regulations just fine.

The fact is, at this point in time, no one has any type of equipment to test the emissions from an outboard engine in the field. So, who's to say if your modded engine makes more pollution, or less?

In case you weren't looking, companies like Mercury, Yamaha and Evinrude are still blazing away with their 2 stroke DI programs like there is no tomorrow. They know that if they build 2 stroke engines, with their performance advantages, people are going to buy them.

I figure that I will be boating actively for 20 more years. I don't see a time when I will not prefer a 2 stroke outboard for whatever type of boat I have. Like I said, it is my preference. I am definitely not alone.

Artie

Good info. To be honest, I was not terribly informed when I bought my most recent motor. When I think about it, I think I let my experience with my old 2 stroke influence my decision and didnt really even give the new 2 stroke technology a consideration. All that said, I still like the 4 stroke I have. You and Pat both gave me good info on my first question and educated me a bit along the way. Thanks guys.