35hp Merc dies at full throttle

[zuidema]

" I have a 1985 3.5hp Mercury

" I have a 1985 3.5hp Mercury that dies at or near full throttle. If I'm at a slow speed and give the engine full throttle, it will run for a minute or two before quiting. If I'm at half throttle or more when I open it up, it dies quickly. I'm thinking this could be a float problem, but I would appreciate other opinions before opening it up. Thanks. "

 

[terry]

you could be running out of f

you could be running out of fuel when you open it up and it starts to die choke the motor if it picks back up its a fuel proplem if it dies you have a fire problem try that and let me know how it goes we can work on it from there

 

[joereeves]

"Zuidema... Although Mercurys

"Zuidema... Although Mercurys are not my line of expertise, your problem is common to any engine. From what you say, I'm assuming that when you apply full throttle from a dead idle rpm, the engine runs at a normal full throttle rpm for a couple minutes. If so, the carburetor would be okay. Carburetors do not come and go. They are either good or bad (clogged or clean).

You state that if you're at half throttle and apply full throttle, the engine dies quickly. This indicates that the carburetor is not being supplied the proper amount of fuel.... at a low rpm, the carb is being supplied enough fuel to obtain full throttle for say two minutes, but at half throttle the fuel being supplied to the carb is only good for a few seconds.

If you have no fuel or air leaks in the fuel supply hose or hoses at the powerhead (check it), I would suspect that you have a failing fuel pump.

This can be easily checked... pump the fuel primer bulb when you apply full throttle. If your problem vanishes, replace the fuel pump. Let us know what you find.

Joe

"

 

[zuidema]

" Choking the motor does bring

" Choking the motor does bring it back to life. The fuel is gravity fed from the tank (no fuel pump), I've replaced the fuel filter and the fuel line on the engine. "