2006 15 HP Yamaha

[Crestliner2007]

Early this year I replaced the water pump. At that time, I noticed a heavy build-up of black, geasy gunk on the inside of the prop. I cleaned it all out using acetone, WD-40 and a pressure washer. Got it looking like brand new!

I've got 30 hours on my engine right now. The gunk is back! What's the deal with this stuff? Is this normal? Should I take the engine in for some kind of servicing? I re-cleaned it again, but it seems to me that this should not build up quite as fast as this?

I don't do much trolling with this engine and do run it at WOT a lot. Each year I average about 60 - 75 hours on this engine. I have Yamaha 10 micron water filter/separator in the boat and use "Star Tron" (by StarBrite) Enzyme fuel treatment in my gas. I also do a full tune-up every year myself. Am I doing anything wrong?

Thanks for any input folks!

 

[robert graham]

Re: 2006 15 HP Yamaha

a few years ago I started using the Pennzoil Marine 100% Synthetic oil in my 90C Yamaha and it smokes a lot less and produces very little carbon or gunk around the exhaust. are you running the correct fuel/oil mixture? how do your spark plugs look? is your engine warming up to a good normal operating temperature? if it was running cold due to a faulty thermostat then it might be running rich and causing the oily gunk. Good Luck!

 

[Crestliner2007]

Re: 2006 15 HP Yamaha

I'm sorry! I failed to mention that this is a 4-Stroke engine. Doesnt' burn oil. When I did the spark plugs in the spring during tune-up, they appeared to be almost new. So I'm not sure just where this gunk is coming from? I do grease up the prop shaft. I'm wondering if too much grease? But what could be "burning"!? It's almost the consistency of chimney soot, if you know what I mean.