76 Mercury 650 dies at high throttle

[Bary0802]

Please help this motor is going to be the death of me, When out on the lake it will idle and go around the lake at low speeds all day put as soon as I try and go faster then say 10mph it dies but the kicker is is that if I pump the primer bulb it will run great meaning its obviously a fuel problem. I have done so much to this motor and it still hasn't fixed the problem, what I have done:

rebuilt carbs
put in all new fuel hoses, internal and external
replaced primer bulb
replaced tank
put in new fuel pump diaphragm
put new clamps on all hoses in case of air leaks
compression is PERFECT
replaced all hose endings from plastic pieces to metal

whats next?

 

[Dave1027]

Re: 76 Mercury 650 dies at high throttle

I think a closer inspection of the fuel pump is in order. Could it be leaking or sucking air?

 

[Bary0802]

Re: 76 Mercury 650 dies at high throttle

yeah I just went out and looked at the pump, the screws holding it in where way to loose I tightened them up hope it makes a difference just need a test run now

 

[Bary0802]

Re: 76 Mercury 650 dies at high throttle

Well the test run was a fail, would stay at high throttle
for maybe 5 to 10 seconds then slowly bog down and die

 

[frankenx]

Re: 76 Mercury 650 dies at high throttle

HI,

I recently bought the same motor and having the same issue. Can you let me know if you have any luck. mine works fine between 2000-2500 RPM but when I hit it to 4000 rmp it does after 5-10 seconds. Also do you know how to setup the reverser lock on this motor?

 

[chum1]

Re: 76 Mercury 650 dies at high throttle

did you pull the fuel hose fittings out of the carbs? there is a bulletin that says to get rid of the finger screens that were installed from factory, they may be clogged

 

[frankenx]

Re: 76 Mercury 650 dies at high throttle

Thanks for the tip. I'll check those screen and if they are there will remove them tomorrow. Also do you know anything about the reverse lock on these motors?

 

[chum1]

Re: 76 Mercury 650 dies at high throttle

actually that was for bary since he started the thread but all can benefit