SHO = white smoke

[BassinLA13]

Two weeks ago while running back to the launch I get a Low Oil Pressure alarm on my 2011 225 SHO (365 hours w/ the rebuilt powerhead in June 2015). Fingers crossed & I put a quart of oil in and it was fine the next day … the following day after a couple of AM runs it produced a massive amount of white smoke (dragster wheelie kinda smoke) when I started her up. Drove slowly back the launch.

Pretty sure I’d blown something I took the boat to a reputable Yamaha mechanic asking for a compression & leak-down test … he also ended up doing a water in oil test. The result: averaged 170 PSI across all cylinders “great” - no oil in water - he did a 100 HR service - plugs, impeller, fluids etc and sent me on my way.

Yesterday after a day on the Cal Delta w/ 6+ smokeless starts - after I get back to the launch & fire her up to load her on the truck (I’m solo) …. massive amounts of white / grey smoke (not just steam) …. wtf.

Side note: the Yamaha digital trim gauge started showing 5-6 bars @ the lowest point when for years it'd always showed maybe 1-2 bars … I can’t see how this would have anything to do with the smoke but it’s a strange coincidence.

Could this be a thermostat issue ? Later in the day when it’s warmer is when it seems to happen.

Any thoughts you guys have would be much appreciated.

[friogatto]

I had white smoke (2016 250 SHO) but the oil on the dip stick looked fine. Slight coffee sludge on the underside of the oil fill cap was the give away.

Not sure what water in oil test they did but Yamaha had my dealer run this test:

Drain oil and leave plug out.
Hook up muffs tight (tape/straps/etc) and run water through motor.
If there is an internal water issue, water will drip from oil drain plug.
I dont know how long they let the water run before seeing water.

Might be worth confirming thats what they did or ask them to perform this test or get further detail from Yamaha for this test.

Result was new powerhead under warranty.

[yam911]

If the motor is left trimmed down when it is stopped then oil can migrate across the piston rings and get into the combustion chamber. It may smoke like a fiend when started. Trim the motor up just slightly when you stop. Then see if it smokes the next time it is started.

Ever seen a perfectly good radial piston engine at start up? It will kill all mosquitoes within a mile. It is the oil in the downward facing cylinders that have gotten oil in them. So much oil in fact that oft times the propeller is rotated by hand before start up to make sure hydrolock won't happen.

[BassinLA13]

Yeah I have to assume that the mechanic did a thorough testing for water in the oil - he's known too be a bit of a Yamaha guru. That said - maybe he missed something (which is my fear) even though I made it clear I wanted the powerhead & head gaskets integrity tested due too the smoke. That said - why doesn't it smoke at all (not a wisp) when it's cold in the AM and then very heavily after the 6-7 start later on in the day ?

Also are compression / leak down tests pretty definitive in revealing a failure ?

Yam911 - thanks I'll def try that.

Thanks!