1978 Mercury 7.5 not getting enough gas at full speed

[Hunter44]

I've been working on a 1978 Mercury 7.5 hp , I rebuild the diaphragm twice , carb was cleaned in CLR for a half hour in a ultrasonic cleaner, then it was rebuild. Took the outboard out on a Jon boat and when I give it about half throttle it lags and then I have to pump the prime bulb to give it assistance and then when I get to WOT and I have to pump the bulb continuously to keep the outboard running. Need help! And have a brand new Atwood fuel tank, new fuel lines and putt a fuel filter on the line as well, did not replace the primer bulb

 

[tpenfield]

Maybe the vacuum hose that runs the fuel pump?

 

[Hunter44]

Tried it this afternoon and the breather hose from the enter of the fuel mixer to the crankcase was lose. We tighted it up and blew the line out. Me and my father ran it again today on a deep vee boat and it ran great from idle to WOT with it at 1/4 choke if not at 1/4 choke it ran like crap and would have to prime the bulb

 

[tpenfield]

IIRC, there are some carb adjustment screws that you can try. Sounds like the mixture is not rich enough for high speed.

 

[Hunter44]

Should I adjust the needle out little by little and push the choke in and tune it that way?

 

[racerone]

Is the motor firing on both cylinders ?---Compression test done ?------Have you checked upper bearing housing and oil seal ?-----Lower crank oil seal is also known to be an issue !