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Mercury 500 50 HP Power Problem

johnno Hi,

I have a Mercury 500 50 HP 1976-1979 model with the symptons as follows:

Starts OK, runs OK for anywhere from 5mins to 20 mins then the motor cuts out while running fast (ie. 1/2 to full throttle). I can then start the motor and it idles OK but cannot apply any throttle beyond just over idle otherwise it cuts out. After leaving it a while it seems to be OK then can apply more throttle and continues to run OK until the symptom appears again.

Any help appreciated and thanks in advance.

2001-06-28
evin300 Sounds like fuel starvation. Have a passenger squeeze the Primer bulb during this condition to force the extra fuel reqd. to the pump, if that works then consider the following:

Try installing a short piece of clear pvc line between the fuel pump and yo

2001-06-28
12Footer I concur with Evin300. But I wanted to add while underway ,with motor giving you grief, remove the gas cap. If it takes off like a drag boat, it's a venting problem. The tank must get air to replace the fuel the motor burns.
2001-06-28
evin300 Good point 12Footer, Could it also be a faulty check valve in the Bulb Primer? Or what if valve doesnt work at all? stuck open? 2001-07-03
12Footer If the check ball doesn't close,the bulb wont pump up hard, Mike.
2001-07-03

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