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Hello,

Last time out I pushed throttle fwd and boat had no power...Couldnt get her up on plane or over 10 mph. Made it back to the dock and checked the plugs. All six where fouled, almost black and it looked like there was oil on them. Pretty sure it wasnt gas on them, but oil. I changed all 6 out and she ran perfect for the day...Next day same thing again, no power, cant plane, or go over 10 mph...Back to the dock and again, plugs fouled. Any thought? could this be a sign of a more major problem lurking?

My only thought was how I winterized the outboard last fall (my first attempt) I read somewhere that it was a good idea to remove spark plugs, spray fogging oil in the spark plug socket, and replace plugs back in until spring. Could this be part of the problem? I am sure it was winterizing fogging oil and nothing else...Any thought...?

It is a 150hp 1995 Yamaha


Thanks

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Hi Ryan,

Are you saying that you left the spark plugs out of the engine the entire winter? If so a big no-no moisture will creep in there and rust the cylinder walls. I assume you mean change/swap the plugs with new ones in the spring.

Back to the oil, sounds like your Yamie could be getting too much oil... causing the fouling. There is a way to calibrate the oil injection system. That should be best left to a very experienced technician. I have had several oil injected outboards (including V6) and never run into fouling issues from fogging oil. Only lots of smoke for a minute or two. Sometimes I forget to change the plugs altogether (like this season...:-) Your Yamie may also be running to rich, which is means carb adjustment.

Also one last thing, excessive engine wear may also cause symptoms like this by allowing too much oil past the rings, but you say after you change the plugs it runs fine. May a good idea to do a compression check or if you bring it to technician, then maybe a leak down test.

Did you recently buy this engine?

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x2 on compression test.

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Also check your fuel system for air leaks. Aerated fuel will cause the oil injection pump to cycle much faster than it usually does resulting in a very rich oil mixture.

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No, I definetly did not leave them out all winter, only took them out to spray fogging oil in then I put the plugs back in...So, from your experience the fogging oil should not have anything to do with this problem, thanks for helping me rule that out.

I do get alot of smoke when I do a cold start, so I would have to agree with you that an adjustment is needed for both oil injection and carborators. Compression test is a great idea also. Thanks for all your good tips...

Ryan

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Hi Dave,

Thanks to you too for the tips/advice. I checked my fuel system (fuel lines, primer ball) and DID find a small leak where the fuel line connect to the primer ball. I hope that will help my situation as well.

Love all the great advice I get from this site!!!