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Posting a reply to: RE: Anyone's 4 strokes "makeing oil"??

Muskie Fishing -> Muskie Boats and Motors

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Shep

Posted 8/17/2006 7:55 AM (#205396 - in reply to #205372)
Subject: RE: Anyone's 4 strokes "makeing oil"??

Posts: 5874

There were some Yamaha 100/115 HP 4 strokes that reportedly had this problem. Improper break in, too cold of thermostat, hard rings, and improper cylinder finish contributed to fuel blowing by the rings, and diluting the oil. Also, if the motor oil wasn't drained properly when changing, some was left in the crankcase, and that also made it appear these motors were making oil.

I believe changing the thermostat to a warmer one helped. Evidentally, the problem has been solved, because I've not heard of this in the last two model years.