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jimmer

screwed up Oil like substance on 25hp Yamaha

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Hey guys

These are a couple of pictures showing where the black oil like substance is coming from. It looks like it is coming from one bolt. The picture of the engine also shows that it is clean inside the cowling.

Hope you can help.

Thanks,

Jimmer

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How about the lower crankshaft oil seal, or, does there appear any water mixed with the oil? Then possibly the head gasket.

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I don't think the exhaust is plugged, it wouldn't run if that was the case would it?

I guess I should add that a piston ring went on the motor within 3 months of buying it brand new. It was fixed under warranty, so I'm wondering if a gasket was damaged when they did the repair. That was a least five years ago.

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I recall seeing something similar on a 100 Johnson and the problem was a semi-plugged exhaust port. Once it was all cleaned out everything was fine. My bro owned the motor.

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I recall seeing something similar on a 100 Johnson and the problem was a semi-plugged exhaust port. Once it was all cleaned out everything was fine. My bro owned the motor.

How would you know if an exhaust port was plugged and what causes it?

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It appears to be burned oil from exhaust.

Unable to verify without seeing it but I would bet it's a base gasket.

The engine needs to be separated from the intermediate housing in order to replace if that is what it is.

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Thanks Bernie, that sounds like what it could be. Not that I'm looking forward to tearing the motor apart. Do you know if I will do any damage by running it like this?

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Thanks Bernie, that sounds like what it could be. Not that I'm looking forward to tearing the motor apart. Do you know if I will do any damage by running it like this?

I have been running mine like that for a few years, I did not want to open it up as it is so old (72) did not think it was worth any rebuild.I will run it till it dies, it owes me nothing.

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I would try snugging up the bolts on the underside. There are six that that secure the powerhead to the base. Three down each side. Clean all visible residue both inside and out and run it and see what you've got.

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I already did that Roe Bag and was hoping that would have solved the problem. Man, I appreciate all the suggestions and advice. This forum is a keeper!

I'll probably run it for the rest of the season and pull the powerhead over the winter to replace the gasket. It doesn't sound like it's something that will damage the engine.

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Hey Jimmer I own a 2002 25 Yamaha two stroke so I am really curious about your problem. I've done a little research and come up with another possibility other than the lower cowling base gasket. If you view the attached link you will see an exhaust manifold which houses two gaskets. (inner and outer) Could be one or both of these are the source of the residue. Try placing a clean cloth or paper towel under the bottom edge of the manifold. Troll with it for a time and see if you can pinpoint the leak. The manifold appears to be water cooled along with the rest of the block but keep an eye out for the possibility of fire. Hopefully there is insufficent heat in that area but be careful.

 

http://www.marinepartsplus.com/catalog/category/yamaha/Outboard/2002/25MSHA/620302860002/

 

 

Let me know how you make out. Some day I might be in the same boat. ;)

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:whistling: ..and that's what 2 strokes dump into the water.

I hear you fisherman, but that's the motor I have. Even when I fix that gasket, it will still be going out through the exhaust.

I looked at a four stroke when I purchased that motor, but the weights kind of scared me off the 4 stroke.

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Hey Jimmer I own a 2002 25 Yamaha two stroke so I am really curious about your problem. I've done a little research and come up with another possibility other than the lower cowling base gasket. If you view the attached link you will see an exhaust manifold which houses two gaskets. (inner and outer) Could be one or both of these are the source of the residue. Try placing a clean cloth or paper towel under the bottom edge of the manifold. Troll with it for a time and see if you can pinpoint the leak. The manifold appears to be water cooled along with the rest of the block but keep an eye out for the possibility of fire. Hopefully there is insufficent heat in that area but be careful.

 

http://www.marinepartsplus.com/catalog/category/yamaha/Outboard/2002/25MSHA/620302860002/

 

 

Let me know how you make out. Some day I might be in the same boat. ;)

Hey Roe Bag

The residue is all on the outside of the moter housing, so I'm fairly sure that it is that single gasket at the base of the engine. I will probably change all the gaskets that I can if I tear it down in the future.

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:whistling: ..and that's what 2 strokes dump into the water.

 

Not all 2 strokes do.

Direct injected are actually cleaner than 4 strokes.

 

Using quality oils that are designed to burn off more completely will also help in older engines.

 

Jimmer it will not likely cause any damage. Just make sure it isn't leaking out water as it may cause a manifold to overheat.

Still be a good idea to verify the problem and get it fixed.

Edited by Bernie

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It's bleeding from the gills pretty bad. <Sigh> You're going to have to hit it on the head a few times to knock it out and stop the suffering. Nice catch though. What were you using?

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I use amsoil 100:1 outboard mixture which is the best I can find. I might just have to check the adjustments on the carbs to ensure it is running the best it can.

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Spoke to a friend of a friend that services outboards and small engines. The source of you black oily substance is an exhaust leak. It could be either in the exhaust manifold or the the crankcase gasket the sits between the power head and the the lower cowling.

An idle mixture that is too rich will increase the amount of residue.If the idle mixture is extremely rich, unburned gasoline will collect in the exhaust ports and manifold. It will eventually saturate the gaskets and leach through. The black for the most part is carbon being rinsed from the manifold and exhaust ports. Long periods of trolling will increase the amount of residue.

He suggested leaning out your idle mixture and snuggging up everything you can get a wrench on the exhaust manifold and engine block.

 

Clean up all of the residue both inside and out with a degreaser or varsol. Run it and hope for the best. If the problem persists then you'll be looking at gasket replacement.

As a precautionary measure I took a 10 mm wrench and snugged up the bolts on my manifold and found them to be quite loose. Each one could be tightened a full turn or more

Good luck, Roe Bag.

Edited by Roe Bag

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