15 hp johnson stalling out

[robertross]

i have a 1981 15hp johnson that will stall out and die at high speed. happens maybe once in a one or two hour time frame. if i open the gas cap on the dynamark gas tank(there is a release of pressure) and pump the primer bulb, the motor starts up. there is no vent screw on the tank. am i vapor locking or is there a problem with the primer bulb? thanks for the help.

 

[wilde1j]

Re: 15 hp johnson stalling out

The tank should be vented ... are you sure it's a release of pressure or vacuum? Try a different tank.

 

[RPJS]

Re: 15 hp johnson stalling out

The tank should be vented, if not a vacuum is created in the tank as the fuel pump sucks fuel out, evetualy the vacuum becomes greater than the suck of the fuel pump.<br />When the motor stops have you checked the primer bulb, if its sucked flat its a sure sign that the tank is not venting or you have a blockage in the fuel pick up pipe.<br />The fact that when you open the fuel tank you hear a hiss would suggest that you have a venting problem.