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Sounds crazy but on my 250 4stroke with 350 hrs, the oil gets changed every 100hr. Just did a change and more oil came out then went in. Can this be dangerous? Whats the cure? It was defently not water, but maybe fuel?
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Oddly enough, this is a common occurence, although not a welcome one.
Fuel is getting into the crankcase and "raising" the oil level.
This fuel dilutes the oil, and consequently, robs the oil of it's lubrication abilities, due to being thinned out and full of a "solvent" ie: raw fuel.
The concurrence of opinions, as to the cause, seems to be that the motor is not running hot enough to fully vaporize the fuel on combustion.
This unburned fuel makes it's way past the rings and into the crankcase.
More concurrence of opinions seems to be that excessive idling and low speed operation are the culprits why not enough heat is built up to fully burn the fuel.
A "fix" or at least a help, is to install a thermostat with a higher temperature rating.
This way, your engine runs a little bit hotter to assist in vaporizing the fuel and getting a more complete "burn".
If the oil dipstick reveals a thinned out film of oil and smells of gasoline and the level is higher than what it should be, change the oil.
The last thing you want is less than ideal lubrication....ie: thin oil, laden with a solvent.....that washes lubrication from the engines moving internal parts. -
Thanks for the response. Can you answer why it only happens to one of two motors being run the same?Comment
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One thermostat may have a problem and is stuck open or opening too soon making the motor run cooler than the other. just a thoughtComment
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There is two thermostats per motor how long since they were changed ? one on each bank.Comment
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Thermostats have not been changed. Only 350 hrs on 2yr old engines 250 4 strokes. Is this typically serviced every few hundred hours?Comment
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have you never read the maintenance charts from Yamaha?http://www.yamahaoutboardparts.com/f...s-th11558.htmlComment
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350 hours in short time is probably ok say a few months or so . but not over 2 years as they dry out and corrosion sets in this the first place i would start for this problem thats all. they are only about 35 bucks . on this siteComment
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