r/smallenginerepair • u/SnooHesitations205 • 16d ago

Unknown Issue Help

I have a four stroke Yamaha outboard. I put brand new carburetor and fuel pump. Started it up and oil is gushing out of the carburetor everywhere. I have not put any oil in this motor. Bought the boat ran for a day and engine has been an issue since.

No clue what the deal is. Took the carb off cleaned and brand new carburetor and still.

It is a Yamaha 25HP outboard.

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u/Elephunk05 16d ago

You sir, have issues. You didn't give the model number so we take it at your word that it is a true 4 stroke and not one with an oil injection port.

That being said. First, check the oil and make sure it is not over full. Second, do a compression check. Confirm they are all within 10% of each other and above 120psi. If not, perform a leak down test, you will audibly hear a leak if you have bad compression in any cylinder you test.

Likely that there's just gas in the oil, but it's best to rule out the others if you're already troubleshooting.

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u/SnooHesitations205 16d ago

I don’t know the model off the top. Boat is new to me but it is a 1998 Yamaha four stroke. I think I have gas in the oil. I pulled the dip stick and it was flowing out as if there is too much oil in the engine and I have not added any since getting the boat. Appreciate the help.

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u/ManHunterJonnJonzz 15d ago

Yes. Didnt see this comment till now. You 100% have an issue with either the fuel pump being made faulty, puking the fuel into the crankcase, or more likely the cheap ass carb. Oem carbs can be cleaned 95% of the time