1986 Force 125 Runs Great for 3 Min at a Time then loses power

[Jthomas997]

When I first get the boat in the water it runs great for about 5 to 7 minutes. Then all the sudden it bogs down to little more than an idle. Then in about 1 min or so it starts to pick up revving a little at a time then out of now where it goes back to full throttle. Then 2 or 3 min later maybe less, it does the same thing all over again. So far I have removed the carb and cleaned thoroughly, as well as replaced gaskets and reset the floats as they were off just a bit. Ive tried adjusting the screws on the carb while running on the lake but this only helps for a short time and it always inevitably starts to cut out again. Ive looked on forums and seen other people with the same problem. They mention that the (vent tube) can be clogged but I don't know where the vent tube is. I'm at my wits end because the boat seems to run beautifully for 3 min at a time.

 

[Jiggz]

It sounds like fuel delivery problem. Before anything else install a clear fuel filter (Fram G2 less than $5 will suffice) between the fuel pump outlet and the carb's inlet. While at it, you might as well check the fuel screen filter on top of the fuel pump to make sure it is clean. Then do a test run without the top cover or cowling. Watch the clear fuel filter:

-If it stays at least 1/2 full at full throttle, the problem is with the carburetors
-If it empties at any given time, there is a fuel delivery problem, i.e. leaky fuel hose (indicated by bubbles in the clear fuel filter), faulty primer valve, faulty fuel pump, e.g. torn gasket, stuck check valves, etc, clogged tank vent or even a semi clogged pick up tube.

The clear fuel filter is primarily for fuel related troubleshooting purposes. Orient it closer to the fuel pump so it is in a semi vertical orientation with the inlet higher than the outlet.

 

[jerryjerry05]

The "vent hose" it is located on the tank and vents somewhere overboard.
​Sometimes the vent is on back of the boat sometimes on the side.

You check for water in the fuel?

The hoses can be affected from Ethanol.
It melts the inside of the hose and can collapse internally.
It also screws up the rubber seals in any inline connectors.
The best bet is replace all hoses and the squeezie and don't put in any inline connectors.
Install a filter(Jiggz) between the carb and pump and a fuel/water separator inline.

If ?? the boat's sat for any time the pick up tube can also get clogged.
Some boats have a filter or screen on the bottom of the tube and it can get blocked.
Check the diaphragm in the fuel pump.

Do a spark check when the motor starts to die.
And a compression check.

 

[Jthomas997]

The "vent hose" it is located on the tank and vents somewhere overboard.
​Sometimes the vent is on back of the boat sometimes on the side.

You check for water in the fuel?

The hoses can be affected from Ethanol.
It melts the inside of the hose and can collapse internally.
It also screws up the rubber seals in any inline connectors.
The best bet is replace all hoses and the squeezie and don't put in any inline connectors.
Install a filter(Jiggz) between the carb and pump and a fuel/water separator inline.

If ?? the boat's sat for any time the pick up tube can also get clogged.
Some boats have a filter or screen on the bottom of the tube and it can get blocked.
Check the diaphragm in the fuel pump.

Do a spark check when the motor starts to die.
And a compression check.

Where is the pickup Tube? Is that the same as the vent tube? I found vent tube last night next to gas tank, long tube running down. I have checked the fuel filter, I have rebuilt the carb, checked the floats, adjusted the carb while running, replaced the fuel pump, and last night I put HEET in the tank for possibility of water being in the tank. Tonight I will get out the Muffs and test the lines with the inline fuel filter.. I think I will also buy a separate gas tank to hook up just in case. The problem is that my house is far out so its not like I can diagnose and run down the street for a part.

 

[Jiggz]

I understand the distance issue, hence you need to plan your troubleshooting steps. The clear filter is almost an absolute necessity and should be left in place after installation for future fuel related troubleshooting. The separate external tank will also help greatly with your troubleshooting. I have one and used it as an emergency fuel tank after the troubleshooting.

I've changed primer bulb more than once not because the bulb is bad but because the check valve was stuck. Always double check fuel connections making sure inlet and outlet connections are oriented accordingly. Finally, the original fuel hose on some of these Force motors came with a quick disconnect. And yes, many people have reported air leaks on them and most of the time just get rid of them or replace them.

The fact the engine goes to full throttle after slowing to idle indicates no problem with the carbs but more on fuel delivery to the carbs.

 

[jerryjerry05]

Blow air through the vent hose.
Don't use compressed air.BOOM!!!

The vent line and pickup tube not the same.
​The pickup tube is in the tank.
That's where the hose attaches to the tank.
It just unscrews and pulls out.

What kind of boat?
You can send the hull# to the maker and ask for info on the tank and equipment.

Most didn't use a filter on the pickup.
But if there is any crud in the tank it can clog the tube,
Install the filter like Jiggz suggested or a water sep. filter and see if it picks up anything.
If they come up clean? Then the tube is probably ok.
Any gunk in the small filter on the fuel pump?

 

[Jthomas997]

Ok so last night I checked the vent line, it was clear. I hooked up the in line filter, it stayed steady, in fact couldn't even get the boat to lose power. The only thing I had done since the last outing on the lake was put HEET in my gas tank. I'm not sure if that fixed it, or if I just couldn't recreate the problem at the lower RPM's because I was using muffs, which I can't run full out. So I guess the next step is to take it back on the lake and see how it runs.

 

[Jiggz]

You'll just have to do some high speed test runs. If the problem goes away, try recreating it by moving the fuel hose around to see if it's a fuel hose connection problem, i.e. with the primer bulb or the quick disconnect. It's probably an air leak on any of the fuel hose connections that gets exacerbated in some positions especially when you steer the boat around.