Black Oil like substance on 25hp Yamaha

[jimmer]

Just wondering if anyone can give me some insight into where this black oil like substance is coming from and if it is a problem.

I have a 25hp Yamaha that is about 5 years old.

I have to clean this stuff off the casing between the engine and the lower unit every couple of trips. It is coming from one of the bolts on the outside of the upper casing. It looks like some kind of exhaust residue and I have tried tightening the bolt, but it just isn't stopping. I don't want to overtighten that bolt and risk wrecking the threads. Any help would be appreciated.

Thanks,

Jimmer

[Roy]

Can you manage a picture Jimmer?

[jimmer]

Will try to get one in the next day or so.

Thanks Roy

[misfish]

Is your boat made for a short shaft and you are using a longshaft?

If your exhaust is below the water,this will happen.

 

Lets see a pic.

[jimmer]

It's a short shaft on the proper transom. The leak is on the lower side of the casing that the cowling attches to.

[misfish]

Oil injected?

 

Check the oil line connection,also check to make sure your spark plugs are tighten properly.Also check the carb. Maybe running rich and not burning off.

 

There has to be a sign theres a leak somewhere.

Edited June 16, 2010 by BrianB

[jimmer]

I'm going to take a picture.

2 stroke.

Not leaking from any lines, thinking there is a seal gone somewhere that the engine is bolted on.

I'll post the picture tomorrow. Thanks guys!