yamaha F300 V6 2012

[captain rednut]

hi has anyone owning this model experienced fuel in engine oil issues, i have been making engine oil at a rate of up to 2 liters in 80 hours. maybe i need to change oil grade?? any feed back appreciated.
i am extremely happy with the engine just would like to solve this mystery.
regards jim

[boats.net]

Need to have compression and leak down test done to see if leaking past rings.
Too large a pitch prop can do it, best to prop on higher side of 5000-6000 rpm operating range at full throttle.
Bad thermostats can do it, engine running too cold makes it run a rich condition.

[rodbolt17]

leak down test and make sure the engine can turn 5800+ with the load you have THAT day.
yes bad t-stats can make it run on the rich side and make oil.
typically its over propping for the load.

[captain rednut]

hi my W.O.T is 5700 rpm and yamaha in oz are telling it would be better to give the motor more load (a bigger prop) to make it work harder??
they just compression tested it and they were happy as all cylinders were even. they are wanting me to try different oils and there synthetic blend.
can i buy hotter thermostats for that model??
im very concerned as im getting low viscosity contaminated oil in 40 hours.
we are mainly operating the engine at 1400 rpm all day which doesn't help this problem.
thanks for your replies.
cheers jim

[99yam40]

That sounds like the problem.
The 4 strokes do not like *****ing all day, need to get it up in RPMs and run hard to help cook the fuel out of oil everyday.
They also need to be broke in properly to seal the rings.

Have them do the leak down test not just compression to make sure the rings are sealing well

[captain rednut]

ok thanks i will do the test and let you know.
regards jim

[rodbolt17]

WOT looks good.
typically we dont want to use synthetic until after the engine is PROPERLY broken in.
at the end of the day try running it above 4000 RPM for at least 30 min.
have a leakdown test done to rule out cylinder glazing or a possible ring gap alighnment.
at that RPM the engine cannot and will not remain hot enough to burn off water vapors. thats a lot of Aluminum to keep warm.

[captain rednut]

hi rodbolt do you think it requires more revs?? i currently run a 17p and with the 19p spare i have i get 5300rpm.
thanks jim

[rodbolt17]

5300 is to low.
5700 is good.
after extended low speed running yu really need to run above 4000 RPM for at least 30 min to heat the oil and the block.
have a leakdown test run to insure there is not a mechanical problem.
compression test wil be useless.

[jeanmich57]

Hi

What's the pitch of your prop and the size of the boat, i just bought a new F300 XCA for my 26' aluminium walkaround and ordered a 14 1/2 x 17 SS Salwater series II prop and i am wondering what's going to be .
Brgds