92 Yamaha 8hp cuts out at full throttle

[iainthardtofind]

My Yamaha shuts down at WOT. If I pump the primer bulb the engine will run fine at WOT. Do I have a fuel pump problem?<br /><br />There is a small inline filter on the way to the pump and carb. I can see an air bubble in there. Am I pulling air somewhere?

 

[Rob E]

Re: 92 Yamaha 8hp cuts out at full throttle

I had a similar problem. It turned out to be the float level in the carb. It needed to be adjusted to let in more fuel. <br /><br />L8R<br />Rob

 

[Xcusme]

Re: 92 Yamaha 8hp cuts out at full throttle

Removing the in-line filter would be the first thing to try. If it's air locked or just partially blocked, it might be allowing only enough fuel to pass for low end performance. If it runs the same with the filter out, disconnect the fuel hose from the carb, put that fuel line in a small container and pull the starter rope. If the fuel line delivers a good flow, your pump and tank hoses are OK. Look next at the carb. If the fuel delivery is not good the only things left are the fuel pump or the tank lines are sucking air. Be sure you look closely at the 'O-rings' in the tank hose ends too.

 

[Paul Moir]

Re: 92 Yamaha 8hp cuts out at full throttle

If that filter is a little white translucent nylon thing with a screen in it, then I can tell you that my uncle's 5hp Yamaha built Merc always seems to have a bubble in it. The engine has no fuel related probems.

 

[iainthardtofind]

Re: 92 Yamaha 8hp cuts out at full throttle

my primer bulb should not soften as I run the motor? or should it?

 

[iainthardtofind]

Re: 92 Yamaha 8hp cuts out at full throttle

looks like the bubble in the filter gets bigger and bigger when I run the motor in a tub. I can't get WOT in tub though.<br /><br />I'm thinking it't might be either the fuel hose connector(aftermarket connector that doesn't fit quite like the original) or the fuel pump, suction of fuel at high idle did not seem very strong.<br /><br />Any help is greatly appreciated

 

[Paul Moir]

Re: 92 Yamaha 8hp cuts out at full throttle

Sorry, the bubble never grew. You can shake it out while priming to make it disappear. Try tilting it vertical, pump the bulb, and send the bubble to the carb. Then see if it re-appears. If it does, there's your problem.<br />Your probably right about the connector.<br />The primer bulb will sofen some when you run the motor.