1997 120hp force fuel problems

[usmc_hemb]

I had just got done rebuilding my 1997 120hp force outboard. It was bored out to .20 over. I finally got it in the water and everything runs great but one thing. While were going at around 3/4 to full throttle for a few minutes the ball loses its prime and i have to prime it and it goes good for a while then it will happen again. Im not sure on even what to check. all the help would be appreciated. thanks

 

[john from md]

Re: 1997 120hp force fuel problems

It could be the check valves in the ball or you can have a pin hole in the hose going to the fuel pump.

Do you have a quick disconnect on the engine side of the hose? If you do, disconnect the line and pump it up. If it bleeds down, replace the line and bulb.

If you don't have a quick disconnect, you can pull the line off at the inlet and screw an oversized bolt in the end and then try the same test.

John

 

[pnwboat]

Re: 1997 120hp force fuel problems

Not sure what you mean when you say the "the ball loses it prime". Does the primer ball go flat, or is it just that you have to squeeze it again to keep the motor going?

Anyways, like John states check the line and bulb. Also check to see if the fuel tank vent is open. If it's plugged, fuel won't flow properly. Have you replaced the fuel pump diaphragm?

 

[usmc_hemb]

Re: 1997 120hp force fuel problems

Well when im going at 3/4-WOT there are times where the ball goes flat and sometimes it just gets a little soft. Basically i just let off the gas and pump the ball and it is fine again for a while. I had just replaced the ball and hose. And the hose going to the pump is very new itself.

 

[usmc_hemb]

Re: 1997 120hp force fuel problems

And yes when i did the rebuild i got a fuel pump kit as well. So all of the parts in there are new as well.

 

[pnwboat]

Re: 1997 120hp force fuel problems

Replacing the primer bulb eliminates it as a cause. You either have some crud in your tank that is stopping up the fuel pick-up tube, or the gas tank vent line may be stopped up. To verify the gas tank vent, try running it with the gas tank fill cap off or just barely screwed on to allow air to enter the tank as the gas is sucked out by the fuel pump.

Also, fuel line should be a minimum of 5/16 diameter. I know in some cases they use 1/4 inch which in my opinion (not that I'm a certified expert in these areas) is borderline. 5/16 or 3/8 fuel line is better.

 

[john from md]

Re: 1997 120hp force fuel problems

When you rebuilt your fuel pump, did you replace all three check valves or only the one that is screwed in? You can pull the pump housing and check to see if the check valves are sticking. Dry them off real good and then push lightly with a thin object like a toothpick or jewelers screwdriver. Do this several times to the poppets in the check valves.

Sticking check valves will cause the symptoms that you are seeing with the ball getting soft.

John

 

[usmc_hemb]

Re: 1997 120hp force fuel problems

I will try and take the fuel pump off and check the valves. I will let you know what the results are. Thanks.