75 HP 4 stroke can't sustain wot

[biology]

I am having issues with this motor. Runs fine at 4000 rpm for a 1/2 mile then sputters and dies. Runs fine at 3000 rpm for 1 mile then sputters and dies. Run fine at 2000 rpn all day. I have replaced everything. New mecury bulb, new line, new filter, new intake on gas tank, new plugs, and today new fuel pumps-$$$. The new fuel pumps made an improvement but not good enough for Canada. What am I missing?

Could the fuel pump change levers be worn so they are not engaging the fuel pumps enough for the higher rpms? How do you test them?

 

[dennis461]

How old is the engine? Hours?
Did the problem start suddenly, meaning it ran fine last month?
Is this the first time running this season?

Can you do a compression check?

The improvement from new fuels pumps, is it real or wishful thinking, meaning, I've changed parts before and was sure it was better, only to find out it was my imagination. :-(

 

[biology]

I think I fixed it this morning. I am going to lake Friday to go wot. After reading manual, my 2000 75hp mecury had 4 inline fuel filters attached to the carbs back side. Two of the filters were completely blocked with debris. This would allow some gas to allow slow speed but not enough to sustain wot. I will know tomorrow.

 

[biology]

took to Lake today, same problem, runs for 1/2 mile then stutters and dies. Took cowling off and the top new fuel pump was very hot. Removed the fuel line and the gas was hot. the pump was not pumping. took apart and pushed the pin in and reassembled the pump. The boat ran 100% for 15 miles at wot. go figure.