Fuel In Oil On A F150 Yamaha

[SEA5KAUAI]

Aloha, I Am Getting Fuel In My Oil On My Yamaha F150txr. The Engine Has About 600 Hours. I Will Check Compression Tomorrow To See If There's A Problem There. Is There Anything Else I Should Be Looking For? Dave

[rodbolt]

compression test will be mostly useless, have a leakdown test done.
with the normal load you run with can the engine turn 5800+ RPM?
will the block actually warm up,possible stuck open t-stat.
does the engine temp sensor actually give the ECU good data?
only way to tell is with a laptop.
that about covers all the ways to add fuel to the crankcase Via the cylinders. other possible methods are from the VST vent line or a defective fuel pump diaphram.
if the engine ECU sees a cold engine fuel is over rich, if the engine cant turn 5800+ with its normal hull load it will make oil as its lugging.
the last cause is simply excessive idle time without periods of at least 4200+ RPM for 30 min minimum.