Random blue smoke on 4 stroke

jloch

Seaman Apprentice
Joined
Apr 18, 2013
Messages
33
So it's a new to me 99 8hp evinrude 4 stroke.
I've had it out on the water 3 times total. Starts great, Runs great, lots of power (for an 8) .
So the first time out after many starts and shutdowns it puts out a cloud of blue smoke out of no where, smoke clears and no sign of
blue for the rest of the day. Second time out fished all day with no sign of blue.
Third time was fine all day, then while idling, poof cloud of blue, then gone and no sign of blue for the rest of the day.
This doesn't sound like rings, does it? Also if it was a valve seal issue it should smoke on start up (did once, but not second time).
external leak burning off? motor seams clean though.
any ideas?
 

jloch

Seaman Apprentice
Joined
Apr 18, 2013
Messages
33
Well I've had this motor out several times now and I no longer think the smoke is oil related.(no burning oil smell and no oil usage)
The motor smokes a lot more frequently now, will run fine at idle and then seem to loose rpm's
and smoke for a few seconds then back to normal (running rich?). It is now starting to backfire at high rpm's also.
 

jloch

Seaman Apprentice
Joined
Apr 18, 2013
Messages
33
So I pulled the spark plugs and the bottom cylinder is definitely showing signs of oil leakage (plug was pretty wet).
Performed compression test (engine was cold no access to water to warm up motor) and compression was
115 lbs in both cyls. Note: I was able to achieve this on 4 pulls in both cyls.
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jloch

Seaman Apprentice
Joined
Apr 18, 2013
Messages
33
Is it running cold check operating temp​
Temp seems to be within specs. My current suspicion is leaking valve seals, but will perform leakdown test
next anyway. Followed by partial tear down during winter.
 

jloch

Seaman Apprentice
Joined
Apr 18, 2013
Messages
33
I realize leaking valve seals won't affect leakdown down test. I don't expect leakdown to show anything unusual, its more a matter of Due diligence before I take anything apart. Also spark plugs have been changed. Could a sticking ring cause such symptoms?
 

Mas

Lieutenant Commander
Joined
Oct 3, 2006
Messages
1,656
Are you removing the motor from the boat after each usage? If so and the motor is laid down improperly, oil can leak into the cylinders and cause the smoking.

Just a thought,

Mas
 

jloch

Seaman Apprentice
Joined
Apr 18, 2013
Messages
33
Motor is removed regularly, Goes from the boat to the stand in an upright position and is never lay'd on its side.
Thanks
 
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