Smoking motor??

[Granny]

I have an older 20 hp Merc that is in good condition and it has ran just fine all year. The last couple times I have had it on the water it has been smoking a little bit. I don't know jack about motors so maybe someone can help me. There is water circulating through so I assume the water pump is ok. Its not a cloud of smoke, but more like a steam....I guess. The portion of the lower unit that is out of the water feels pretty warm but not extremely hot to touch. Is this normal? The last two times I have been out, the air temp has been really cool. Would this have anything to do with the smoking? The motor still runs fine, I just don't want to blow it up. Thanks for any help.

[Norco]

The problem may be that you are running your oil a bit rich?? I had a simular problem with my 2 stroke 25hp Merc. I changed the slug and wire cap and make sure that I have fresh 87 octane gas and she runs great. If you don't find an answer that satisfies you I would go to iboats.com, go to the forum for outboards and you will definetly find your answer. Good Luck

[SWMuskeye]

I don't know if it is a mixed gas motor or non-mixed, but this happened to me in a non-mixed motor, I put in more fresh oil and my problem was solved. Sounds like your situation may be a little more troublesome.

[Granny]

The oil and gas are mixed in the can. I thought the mixture could be off a little but doesn't that cause more of a blue cloud of smoke instead of a steam?

[Guest]

If you haven't changed your water (pump) impellor in the lower unit that pumps the water through the engine, have it replaced. These impellors need to be replaced every couple years with normal/above normal use!

I have a 15hp Honda 4-stoke that had a worn impellor and that engine smoked due to over heating!

Water WILL still circulate, but not properly! What happens is the impellor is made of rubber with "paddles" that pump water up. The paddles wear out and flatten with memory which does not pump water upwards to the engine with enough force.

This might not cure your smoking issue, but it should help the engine, big time. I switched to Amsoil synthetic lube and noticed a lot less smoking and stinky fumes. Expensive, but worth it IMO.

[Guest]

I would venture to guess it is old oil and sludge build-up, too much goo in the tank or carb?

Dump and flush the tank, then re-mix a factory recommended brew. If it still smokes but runs overall well at full load and idles well, it may be a bigger issue then fuel. Like a stuck ring or something internal? May be as simple as buggered up plugs too? See if the plugs look oily or fried once?

Your carb jets may be all buggered up too? You could add some Sea Foam to the mix of the fresh tank and see if it cleans it up.

If you are getting a good flow through the cooling jacket it should not be heating up. If the indicator stream is very hot even at a starting idle, I would get the impeller replaced ASAP. The impeller is a cheap & easy maintenance deal and can save you much bigger bucks in the long run.

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Ed "Backwater Eddy" Carlson

Backwater Guiding "ED on the RED"

[Surface Tension]

Granny Its most likely just vapor that is white because of the cold air. Kinda like a cars exhaust in winter. Usually the tell-tale stream will not be as strong when the impeller is going. However there could be blockage and still a good stream. Replacing the impeller will give you peace of mind. If your not sure how to replace the impeller get a manual. You may as well drain the gear oil and if theres water there replace the seals while your at it.

[Granny]

The indicator stream is fairly warm as soon as I start it up. It isn't scorching hot but it is pretty hot. I don't think it has anything to do with the gas or oil burning improperly. From what people have posted I think its the impeller. Is this something easy to change or should I leave it up to a pro?