1986 Force 125 losing power on full throttle

[SkiDad]

good luck! - I'm guessing your boat is a cobra by the looks of it. I would still try the portable tank - you can probably pick one up on craigslist for cheap.

 

[pnwboat]

Might want to replace the three check valves in the fuel pump. They're known to stick. Two of them are easy to replace, the third check valve is pressed in that deep recess and you have to destroy it to get it out.

 

[binghaml]

If the tank and the pick up tube are in perfect condition, then you are basically left with three items to troubleshoot, i.e. fuel pump, primer bulb and the separator. You can just by-pass the separator for now and see if that will fix the fuel delivery problem. If problem persists, then it is time to try another primer bulb (make sure it's connection are oriented properly) while continuing to by-pass the separator. If problem still persists then there is only one thing left to conclude, the fuel pump is not delivering the right amount of fuel.

In the pics of the fuel pump, you did not show the other side and I was wondering if you have the gasket also that goes with the diaphragm. Additionally, double check the fuel filter (screen) on top of the fuel pump to make sure it is there and clean.

I think you may be on to something with the gasket... I remember replacing it when I replaced the diaphragm, but I don't remember seeing it anywhere when checking the pump the last few times! It's possible that it is stuck to the engine side, but I need to double check that! I didn't even think about that gasket until you said that.

It's been a couple months since I've checked the screen filter, I'll check it again too.

I'll do those checks first, then I'll start bypassing things. Hopefully I can get out to the boat after class today!
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good luck! - I'm guessing your boat is a cobra by the looks of it. I would still try the portable tank - you can probably pick one up on craigslist for cheap.

Thanks! What are some identifying features of the boat's model/trim? I know it's a bayliner capri, and I'm guessing it could be a runabout, and have the numbers 1950 in the name? This is just from my googling, the previous owner only had an owner's manual for the motor - not the boat. It seems like it was probably a really cool boat back in 1986. It also seems like the original owner just used it a couple times then let it rot in their driveway without a cover...

I will keep an eye out for a cheap portable tank, or see if I can borrow/rent one from somewhere. I just would hate to buy one to use it once and possibly find out nothing, then have it sit around useless forever haha. I may end up with no other option at some point though.

Might want to replace the three check valves in the fuel pump. They're known to stick. Two of them are easy to replace, the third check valve is pressed in that deep recess and you have to destroy it to get it out.

This is starting to look like a strong possibility. The only other visible damage to the fuel system I've seen in all my time going through it was the fuel pump diaphragm. It would make sense that other parts of the fuel pump didn't survive whatever tore the diaphragm as well. I'll bypass a couple things first, but if it gets narrowed down to the pump, I bet it is these valves.

 

[Jiggz]

"I will keep an eye out for a cheap portable tank, or see if I can borrow/rent one from somewhere. I just would hate to buy one to use it once and possibly find out nothing, then have it sit around useless forever haha. I may end up with no other option at some point though."

It is not actually a total loss. In my case, I actually have a 6 gal PGT with a spare set of hose and primer bulb. I use it as an emergency back up just in case I ran out of gas from the main fuel tank. Every season I try to empty it to make sure the fuel stays fresh. Usually before the end of the season I ran it using the PGT just to burn some of that gas. I keep the PGT under the port stern while the battery is under the stbd stern.

 

[binghaml]

I suppose it would be more advantageous to have a PGT instead of just one of my 5gal spare tanks (of which I now have four...) since a PGT would have its own plumbing as well.

Small update, the fuel pump gasket is still there, it was just stuck on the engine side but it is in good shape. I didn't get a chance to check anything else, only had about 5 minutes at the boat today. Will update by this weekend, possibly sooner, on what bypassing the separator and/or primer bulb does.

 

[binghaml]

I don't have a lot of time to write this, so I may elaborate later. Anyway, today I was able to get some fuel line to by-pass the separator and the primer bulb. I first bypassed both, to isolate the fuel pump. Good news! the fuel in the clear filter barely dropped at 3k rpms, and shortly after it dropped it filled back up - within 2 seconds.

I put the primer bulb only inline. The fuel level dropped at 3k rpms. So it was the bulb! I went and got an exchange from the place I purchased it. I got back to the boat and realized that I had been using a bulb for 1/4 inch hose the whole time! I don't know how I didn't notice this. So now I'm waiting to get to the store to buy a 3/8 bulb to match my fuel line. In the mean time, I have an almost brand new 1/4 inch one (mercury) if anyone is interested for $20 haha. Only pumped 3 times!

Once I get the 3/8 bulb installed I will test again, but I'm pretty sure that this was the problem. The only thing that doesn't make sense to me, is that when I replaced the fuel pump diaphragm a few months ago, I had the 1/4 inch bulb installed. It ran great for a couple of hours. How did this happen? Do they shrink slightly with use or something? It was a problem that got worse as I tried to run it, but I suppose that could have been other factors, like the low battery at the time.

Anyway, I'm really excited, and my hopes are up right now that this mystery may be solved. Will post back with an update once I get the 3/8 bulb test done.

 

[SkiDad]

I don't think the diameter was the problem. I would say that the squeezy is defective.

 

[binghaml]

I don't think the diameter was the problem. I would say that the squeezy is defective.

I should have included in my previous post that when I installed the new primer bulb (1/4 inch) then ran the motor at 3k rpms, it too caused fuel loss in the clear filter. Because of that, I'm thinking it must be diameter related, even though a defect would seem to have a larger impact. I am planning on picking up a 3/8 bulb tomorrow after class and then testing it. So if all goes well I should know tomorrow if it was in fact the problem.

 

[jerryjerry05]

NEVER, EVER EVER EVER pressurize a fuel tank!!!IEVER!!!
The act can cause static electricity and the fuel can go BOOM!!!


I run BOTH of my 85's on the same 1/4in feed.
The feed line is 11ft long.
Both go through a water sep filter and both have inline small particle filters between the pump and the carb.
I ran a 225 EFI on 1/4in hose with no trouble.

Now IF??? the hose is old or weak it would/could be trouble. But yours is new.
Vent line?

The clear filter DOESN'T have to be full for it to function.
Sometimes air gets in there and it stays.

What's the compression on the motor.
You said it was good but the #3 cyl operates the pump.
They all should be about the same.
Is the gasket behind the pump there?
What condition?

 

[binghaml]

Update: I've put a 3/8 bulb on there and the fuel level does not drop in the clear filter. So, as far as I can tell, it is ready to take to the lake to see if it actually works, as I can no longer re-create the problem in my driveway with the 3/8 bulb installed.

I find it strange that the diameter apparently made that much of a difference. Unless I had two defective bulbs in a row, that both worked correctly when you blow through them, then I think the jump from 1/4in to 3/8in was needed. I feel like a dunce for installing 3/8in line, and a 1/4in bulb but at least that is corrected now.

I will report back after I make it to the lake.. Hopefully this weekend, just waiting for the Seattle rain to stop..... haha

NEVER, EVER EVER EVER pressurize a fuel tank!!!IEVER!!!
The act can cause static electricity and the fuel can go BOOM!!!

I haven't, I didn't have the tools or feel comfortable doing it. I also read that it can "pop" your tank if you're not careful.

I run BOTH of my 85's on the same 1/4in feed.
The feed line is 11ft long.
Both go through a water sep filter and both have inline small particle filters between the pump and the carb.
I ran a 225 EFI on 1/4in hose with no trouble.

That's strange.. According to the shop I went to (two shops now actually), they both say that around 80hp is where you typically see a switch from 1/4in line to something bigger. I'm wondering if maybe it has something to do with the difference in those motors' efficiency, vs my motor's efficiency - or maybe EFI vs carbureted. If my understanding of the fuel systems is correct, running EFI would be much easier to get away with small hose since you have pressure to push through. My motor is carbureted, so it would have less power to move fuel through a line, thus needing the larger diameter.

Now IF??? the hose is old or weak it would/could be trouble. But yours is new.
Vent line?

Vent line is new. Old one wasn't plugged either.

The clear filter DOESN'T have to be full for it to function.
Sometimes air gets in there and it stays.

But there does still need to be at least as much fuel flowing in, as flowing out, no? The problem I was having was the fuel level was decreasing, and eventually it would be empty, save for a trickle of fuel going through. In other words there was more going out than coming in. It never was completely full though, only about 3/4 at most.

What's the compression on the motor.
You said it was good but the #3 cyl operates the pump.
They all should be about the same.
Is the gasket behind the pump there?
What condition?

I don't have the compression numbers. I took it to a mechanic and they said that all cylinders had good compression (they were working on / checking other things as well). I would assume that means that the cylinders' numbers are close to the same, though I guess it would depend on your definition of close.

The fuel pump gasket is there, it is in good condition. It was just replaced a few months ago and has had almost no use since then.

 

[jerryjerry05]

Your 125 on any Bayliner came with 1/4in.
I rigged hundreds and they all had 1/4in.

You got the bulb in right?
They can be bad right from the box.

Pop the flywheel and see if there are any discolored spots on the stator.

Is it possibly overheating?
Test the buzzer under the dash?
Test the temp sender using an OHM meter.

 

[Jiggz]

If the clear fuel filter stays full or at least maintaining 3/4 full, you know for sure fuel delivery will not be the problem if your original problem persists. Based on the diagnosis you did earlier and eventually correcting the problem, your original problem should be resolved. If not, at least now you know it is not fuel delivery problem. Post your test results so this thread can be a reference to others especially if it resolved your original problems.

 

[binghaml]

Your 125 on any Bayliner came with 1/4in.
I rigged hundreds and they all had 1/4in.

You got the bulb in right?
They can be bad right from the box.

Pop the flywheel and see if there are any discolored spots on the stator.

Is it possibly overheating?
Test the buzzer under the dash?
Test the temp sender using an OHM meter.

Ah, well mine is running 3/8in now. Maybe just having varying diameters inline for the fuel line created some turbulence or resistance for the fuel..? I also wonder why both shops were telling me something different? Not questioning knowledge - just curious if there's a factor in deciding fuel line diameter other than motor size. I would assume EFI/carb would play a role.

All three bulbs (original 1/4in installed a few months ago, it's replacement 1/4in bulb just earlier this week, and the 3/8 one yesterday) have been installed correctly. As far as I know, Mercury isn't some no-name brand. Their bulbs weren't the cheapest, so I wouldn't expect two defective ones right out of the box, in a row. I suppose anything is possible though.

If my issue persists, I will check the stator. That was my next step at one point, until the "no-spark" disappeared and it started firing on all cylinders again.

I don't think it's overheating, but I'm basing that on the fact that I have a "tell" on the coolant line. Basically it just shoots water out the engine cowling if there is water flowing through the cooling system. It's never seemed to have an issue in that area - always a steady stream of water. Plus this issue was happening at any point in operation. Within the first minute of starting, or even after about 30 minutes of running. It didn't seem to be reliant on engine temp.

I will test the buzzer and temp sender if my problem persists.

If the clear fuel filter stays full or at least maintaining 3/4 full, you know for sure fuel delivery will not be the problem if your original problem persists. Based on the diagnosis you did earlier and eventually correcting the problem, your original problem should be resolved. If not, at least now you know it is not fuel delivery problem. Post your test results so this thread can be a reference to others especially if it resolved your original problems.

I'm hoping it is all solved, but even if it isn't, at least I can move away from looking at fuel problems. I'll absolutely post test results. These threads are infinitely helpful when reading up on a problem. I'm trying to be thorough and mention everything I've done for any future readers - I sure appreciate reading a well-documented thread of someone experiencing, then solving a problem I'm experiencing.


I'd also like to thank every one who replied to my problem. There aren't many people out there who would help an internet stranger with their boat problems. I truly do appreciate it. Even if my original issue is not fixed, I've been able to make great strides toward solving it and it's all thanks to you guys.

 

[binghaml]

Good news everyone! I took the boat out this weekend. It ran great, 0 complaints here. It was able to maintain full speed for as long as I wanted, and never had any problems. It seems that the primer bulb was the problem after all!

Thanks again!

 

[jerryjerry05]

Great.
I bought 3 bulbs (Tempo) and they were bad right out of the box.
I don't buy them unless they are the only thing there is.
I wonder who makes Mercury squeezies??

 

[Jiggz]

Outstanding. And thank you for posting back the positive results.