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Joe, Marine Mechanic
Category: Boat
Satisfied Customers: 7251
Experience:  ASE, electronics, Marine mechanical and electronics, pwc, wiring, all around repair tech,
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Yamaha 70HP oil injection engine. This engine has set a

Customer Question

Yamaha 70HP oil injection engine. This engine has set for about a year. Prior to that it ran perfectly. Boat is a Bass Tracker 19 footer. Always before the engine would turn up to 5800 RPM. Now it will only run up to about 3800 RPM at about 1/2 throttle. Throttle above that does nothing. Examining the carbs with the air filter off all three are opening full. We cleaned the on the engine fuel filter replaced the inline gas filter with a new one. Replaced the spark plugs. The Clear Inline Fuel filter never fills with Gas. Actually it shows only a small amount of gas in the filter. The fuel is clean and new. Boat Gas only. Is it possible that the squeeze bulb is restricting the fuel? Is is possible the fuel pump is not sucking enough fuel? Is it a Carb issue? The Engine has always been run until it ran out of gas by removing the fuel line from the tank. Engine run until it quit. So any ideas where to look for the problem?
John Goller
Submitted: 1 year ago.
Category: Boat
Expert:  Joe replied 1 year ago.

Hello John,

Thank you for allowing me to assist you, my name is Joe and I will be happy to assist you with your concern today.

Using an external portable tank connect to the motor and see if the problem is corrected, if so then you know you will have a problem between the tank and the motor, a bad ball will not correctly prime/purge, there can also be leaks allowing it to pull air but not spit fuel, there is also a valve but before getting to that please remove the fuel cap and see if the problem corrects, if so then check your vent screen on the side of the hull as wasps and other things are known to clog them, corrosion can also take over and block off the vent opening.

Please proceed with that and let me know your findings.

Thank you!
- Joe

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