2008 yamah f75 4 stroke running problems

[hrzracr23]

Hello all I have a 2008 Yamaha f75tlr 4 stroke. The last few times I have taken the boat out it idles rough and sometimes stalls, when I bring up the throttle its like it only runs on 3 cylinders but the 4th will come in and out creating a surge. once up on plane it runs good for the most part, to about 3/4 throttle anything past that and the motor about dies out and has no power until I bring the throttle back down to 3/4 or less. It has fresh ethanol free gas, the plugs were changed last season. any help would be appreciated.

 

[hrzracr23]

*Update* replaced all fuel filters, and spark plugs. boat ran great for about 30 minutes. Then it bogged down and stalled, would not start back up. When I tilted the motor all the way up fuel began running out the intake. I pulled the dipstick and fuel/oil mix shot out. When I got it back to the lift I drained the oil and it had about 3 gallons of oil/fuel mix in the crankcase. What could cause this ?

 

[99yam40]

is this a carb motor or an fuel injected one?
fuel pump leaking or maybe injectors are the only ways I can think of

 

[hrzracr23]

its fuel injected

 

[99yam40]

well in that case,
fuel pump leaking into crankcase or maybe injector stuck open and dumping fuel would be something to look into

 

[hrzracr23]

i'll check the fuel injectors, where would a fuel pump be able to leak into the crankcase?

 

[99yam40]

not sure if that 4 stroke has lift pumps that could cause this problem of not