fuel related problems

[ezymny19]

I've searched all over this forum trying to find anyone that may have a problem similar to mine.
I have a 1995 Force 120hp. Outboard is on a 17ft pro-gator bass boat with a built in tank.
My problem is when I pump up the primer bulb for the fuel it gets hard and it stays that way and I can start the motor fine and it runs great at idle/half throttle/wide open. I can run down the lake and fish for an hour or so and when I get ready to go to another spot the motor cranks right up and runs for about a minute till it runs all the fuel out of the carbs and then it dies. I always end up having to go back there and pump the bulb back up and it takes off and runs great, but if I stop for awhile I will have to most likely do that again.
Ok, originally I suspected the primer bulb, replaced it twice, finally got a good one on there. That didn't get it so I replaced ALL the fuel lines and fuel filters and made sure all the hose clamps where tight. Still didn't get it. I don't think it is the fuel pump because it runs good at all speeds once you get fuel up the lines. I have not noticed any fuel leaking from places. I do have the fuel in the carb covers from tilting the motor up while I'm fishing and trailering.
I'm stuck, the only two other things I can think that it could be is if somehow something is broken on the pickup tube going down in the tank or maybe the float needles on the carbs are bad. I think if it was the pickup tube than the bulb would never get hard because it would be sucking air.

Any help at all would be appreciated. About to pull what little bit of hair I have left out over this deal.
Thanks,
Matt

 

[pnwboat]

Re: fuel related problems

What style of pump do you have? Is it square or kind of shaped like a figure eight?

I wouldn't count out the fuel pump. Sometimes the rubber diaphragm gets stiff and hard with age. It's a relatively cheap and easy to change.

What size fuel lines are you running? My 125HP had 1/4 inch lines originally. I had some fuel supply concerns so I went to 5/16 lines and have had no issues since then. Some folks even use 3/8 lines.

 

[ezymny19]

Re: fuel related problems

Thanks for replying, my fuel pump is the square kind and I replaced all the fuel lines with 3/8" except the two short ones that are right there at the pump, they are still 5/16" but I did use new hose on them also.
I noticed that the pump kit is pretty cheap too, Are there any check valves inside that thing or is it just a diaphram? The guy I bought it from told me that the only thing that he ever had to replace on the motor other than the normal stuff (sparkplugs, lower unit oil, filters) was the fuel pump.
Surely there is some check valves or something in the pump too, maybe he just swapped out the diaphram?
This motor just runs so good.
Thanks,
Matt

 

[pnwboat]

Re: fuel related problems

All of the kits that I've ordered for the square pumps included the check valves.

I'd also take a look at the vent for the tank. Normally if it's plugged, the motor will not run well. It'll be starved for fuel. You can test by opening the gas cap after you've been sitting. If you hear any air sucking in, then I'd say you have a problem there. Seems like you have an unusual situation so I wouldn't rule anything out.

 

[ezymny19]

Re: fuel related problems

you're right I'll check the vent for the tank next time I go fishing this week, As inexpensive as the fuel pump kit is I should just do that whole deal anyway. I read something in another thread about the needle and seat for the floats in the carbs possibly causing fuel to leak back out, but how is that possible? I don't guess I understand how that would work, I would think that if the needle and seat for the float was not sealing off, worse thing would be flooding and having fuel everywhere. That's not happening with my motor.
Do you think I should try and take out the pickup out of the tank too? Or do you think there could even be a problem there? After talking to you, I hope it's the fuel pump.
thanks for all your help,
matt

 

[pnwboat]

Re: fuel related problems

Only thing that I can think of in the carburetors themselves that would cause your symptom is if a needle valve was sticking closed. I guess it's possible. Again, replacing the needle valve and fuel bowl gasket are cheap and easy to do. Checking float level after changing needle valve is also simple to do. Also make sure carburetor throttle plates are in "sync" after removing carbs and putting them back on.