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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Our 2010 Yamaha 90 hp (4cycle) starts & runs great minutes

Customer Question

Our 2010 Yamaha 90 hp (4cycle) starts & runs great for 15 minutes or so & then dies down to idle or stops. It will continue to run if the primer bulb is continuously pumped.
We tried an alternate fuel tank, cleaned the fuel filter, checked the fuel lines and just tried a new fuel pump.
It runs fine out of the water with the new pump (which it would not do before) but eventually dies, just as before.
Is there some sort of fuel shut-off to protect the engine if the oil pressure is low, engine runs hot, etc.?
Submitted: 1 year ago.
Category: Boat
Expert:  Jeff G. replied 1 year ago.

There is no fuel cut off.Since you ran it on another tank that rules out the boats tank. Did you also swap out the fuel line?

You have a restriction in a fuel line going to the engine. This is probably what caused the fuel pump to go bad. You will need to check all the fuel lines for interior degradation. We are finding the ethanol is destroying the fuel lines from the inside out. Many lines have an inner liner, this is to meet EPA guidelines. What happens is this liner fails and restricts the fuel. The other thing is the line softens and internally collapses.

If you have black rubber lines, rub them and if your hands get black on them, change the line.

Pull any fuel connectors from the fuel lines and look inside the line for deterioration. Finally check for any kinks caused by soft lines.

If you find bad lines, which I suspect you will, replace the lines with marine grade lines.

Post back what you find.