1986 75hp Mercury fuel issues

I have a 1986 75hp Mercury that will only start if I pump the primer bulb so tight that I hear fuel spew at the carbs and the bulb softens.The motor may run fine the rest of the day or 5 minutes.If I choke it,the motor seems to try to idle up.This has been ongoing problem and I've replaced the hoses,primer bulb,fuel pump,and cleaned the carb with new carb kits added.It seems to be worse if I trim the motor up much. Pump the bulb until it spews at carbs and it'll do fine again.Any advice or input will be greatly appreciated.

Re: 1986 75hp Mercury fuel issues

I would first check the fuel line system for any air leaks than if the primer bulb is not within a foot of the motor connection, move it so it is. if you still have trouble run the fuel hose straight to the fuel pump bypassing the motor connection to see if that needs replaced. If the primer bulb is going soft then replace it with a Merc bulb as the aftermarket bulb check valve is not working as it should. This can at times be fixed by placing the bulb so it will stay in a vertical position with the arrow pointing to the sky. Check that the float levels are correct and that they cut the fuel flow off and on as they should. Worn inlet needles and seats can and will stick if worn bad. Reset the carbs with the idle jets 1 &1/2 turns out from lightly seated and adjust them in till the motor stumbles, after it has reached running temp, then back them out till it stumbles. Now turn them back in not quite half way. See if the motor will take off when it is given fuel. You might have to back the idle jets out a screwdriver blade thickness at a time till the motor will go without any hesitation. JMO
Oldman570

Re: 1986 75hp Mercury fuel issues

Thanks so much for your response!We're getting badly needed rain here,and not able to work on the motor today.First chance,I will do as you suggested and let you know how it worked out!

Re: 1986 75hp Mercury fuel issues

what were your results? I just got a 75 hp merc and I know I have 2 issues, one electrical, the secong fuel to top two cylinders...what were your results and what did you do to correct the problem?