Home › Forum › Ask A Member › Help on 1996-2000 OMC 9.9/15 HP FOUR Stroke › Re: Help on 1996-2000 OMC 9.9/15 HP FOUR Stroke
One thing four strokes do like to do is put fuel in the oil. This can come from a variety of things, but usually starts from a cold running engine. Most manufacturers called it "motors making oil" during the early years. Yamaha calls it "oil dilution" now on their four strokes. If you do have a bottom seal out if most likely is caused by being bathed in fuel for an extended time. If the seal has seen ethanol blended fuel just that much worse. You may need to look for other problems while you are in changing the seal if you have to go that far? Ring wear, bearings, etc? If the oil was diluted far enough lubrication goes away in a hurry! All four strokes suffer from this and a cure has been tricky. Just running the motor hotter is difficult because of deposits (salt) cooking out in the water jackets. It’s not like a radiator on your car! Just something else to think about before you go 4stroke crazy. Of course they are much more complicated and costly to repair as people are starting to find out. Our old/ antiquated 2strokes are looking better every day!
Dan in TN