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1978 mercury 80 hpfuel bulb goes soft

F

felderlostnspace

Member
"engine will start acting like

"engine will start acting like it is running out of fuel.i check the bulb and it is soft.can pump the bulb and the engine will run as long as i keep the bulb pumped.it has a new fuel line and bulb and i have rebuilt the fuel pump.any help would be great and thanks in advance for any and all responses.thanks,Bill"
 
"would the check valves in the

"would the check valves in the fuel pump ahve any thing to do with the problem i told you about above.the reason i am asking is i have not been able to find the 2 check valves(small round rubber that has slots in the middle of them)i gues they are check valve or bleed back valves.help please.thanks again,Bill"
 
"Its probably the pickup in th

"Its probably the pickup in the gas tank. If the pickup doesnt stick all the way to the bottom of the tank, the gas will drain back in the tank. The bulb will then be soft."
 
Thanks for the response.i will

Thanks for the response.i will look at this after church tomorrow.i am hoping it is that simple.any one else?thanks in advance.Bill
 
"ok.i checked the fuel pick up

"ok.i checked the fuel pick up tube in the gas tank and it is ok.i have rebuilt the 2 carbs,checked the coils.replaced the trigger,spark plugs and wires.the motor starts right up and the bulb is firm.i can throttle to 3/4 and the boat planes out great,runs fine,but after about 1 minute the motor starts sounding like it is bogging down.i can feel the bulb and it is getting soft,i can pump the bulb and the engine picks up rpms and speed and seems to run fine again and then again after about a minute the motor will start bogging down again until i pump the bulb.i have rebuilt the fuel pump also but did not replace the check valves due to nobody having them.do these check valves have any thing to do with it?please help.thanks in advbance for any and all responses.thanks again,Bill"
 
"hello,anybody out there or ha

"hello,anybody out there or have i thrown something out there that is not fixable?please help.any suggestions would be great and thanks in advance.Bill.i am lost,look at my user name.thanks again"
 
sounds like a fuel problem for

sounds like a fuel problem for sure.Now the fuel pump is driven by crankcase pressure / vacuum pulses and if there are bad reed valves/ bad rings/ bad labyrinth seal on the crank you will have problems there.Other problems could be too small/long a fuel hose and restrictions in hoses on the motor.Fuel today has a habit of attacking " older " hose material so take it one step at a time.Use a flashlight and look into the carburetor bores and you might be able to determine if the upper or lower one is at fault.
 
"thanks for the response.i hav

"thanks for the response.i have checked the compression and it is 115 on all 4 cylinders.i have a all new fuel lines and bulb from the fuel tank to the carbs.i have rebuilt both carbs.i am sure,well maybe hope it is simple but it may be the reed valve as you mentioned.i heard that is a major repair.i wonder how you check a reed valve.thanks for the response.i'll keep digging,Bill"
 
Cylinder compression has nothi

Cylinder compression has nothing to do with crankcase compresion!Do the flashlight test to see if there is blockage to one carburetor.New valves for the pump should be easy to get / install.
 
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