Yamaha 90HP 2002 runs rough

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boggyboy

Cadet
Joined
Apr 21, 2010
Messages
7
My outboard runs rough intermittently. And when it is running rough there is a significant drop of power.

This problem occurs at various throttle settings including full throttle.

The switch to rough running mode can happen anytime and can last for several minutes

At full throttle, my pontoon boat can reach about 30mph. When my motor swaps to its "rough" mode, the speed will drop about 10mph.

Suggestions much appreciated!
 
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robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: Yamaha 90HP 2002 runs rough

Check your fuel delivery system starting at the pick-up tube in the tank, fittings, primer bulb(2 check valves in bulb), fuel quick disconnect on front of motor, fuel filter/O-ring, fuel pump, drain each carb for water or debris in float chamber. Check your bottom cylinder spark plug for wet fuel condition caused by faulty fuel pump diaphragm. You may have to have carbs cleaned. Install a fuel/water separator on fuel line between primer bulb and motor. Good Luck!
 
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