125hp Force dies after a few seconds at WOT

[Zink357]

Need some suggestions from the experts here on where to look.

I made a pretty bad judgement call and overloaded my boat this weekend. At WOT it could barely get going at all and it was working very hard. I’m afraid of what that actually did to it. Well on our trip back to the landing it died after maybe 1 minute. To start it again I had to choke it and give it some throttle in neutral. It started but same thing happened again once I got going again. So we basically idled all the way back.

So so I took it out solo to see what the real issue might be and same thing happened. Got up on plane at WOT and after 20 seconds it died. Basically seemed like fuel just shut off.

My questions are:

1. Could it have something to do with the fuel tank vent? It is on the side of the bow and I would bet several waves came up and covered it completely when I was overloaded. I unhooked it from the gas tank and blew compressed air thru it and it was clear.

2. The engine doesn’t seem to be running as strong now but it still got on plane ok and seemed pretty strong. Could I have done something to it by making it work so hard under that load?

3. Is it possible it is something as simple as a fuel delivery issue like the pump or something and it is just a coincidence that it happened when I overloaded it?

 

[Nordin]

I would suggest you to check compression and spark at first.
If that checks out good then the engine can be tuned up.
right on.

Check and change the fuel pump diaphragm, it is simple and cheap maintenance.
Also put a clear inline fuel filter between the pump and the carbs.
This will make troublshooting much easier.

Compression should be 140-150 PSI but 120-130 PSI is okey.
Most important is that all cylinders are equal, not more then 10% in difference

 

[Zink357]

Going to grab a compression and spark tester and start there. Will the cheap ones work good enough or are they junk?

 

[foodfisher]

The vent tube should have a loop in it to prevent water acces to the fuel tank. Got loop?

 

[Zink357]

Not sure. It is tucked in behind the walls so I can't see it. No water came out when I blew air through it tho.

 

[jerryjerry05]

When the boat was made, they installed the vent hose and the chances of it straightening out are almost none to zero.
The bugs can get in and clog it, but if you blew through it I wouldn't worry about that.

Compression, "Cheapo Tools" = crappy results.Harbor Freight some tools are ok. The comp tester is usually wrong.
You'll get results but not usually good.
The results if all 3 are about the same?? GOOD!!
They can be 75#(should be 150#) as long as all cyl. are close.

 

[foodfisher]

One more test to eliminate bad gas, run on a portable gas can with known good gas.

 

[Zink357]

Tested the compression and got 120 in all 4 cylinders. Pulled the fuel pump off and it seems fine?? No tears in the diaphragm and it’s firm. Should it be firm? I guess firm isn’t the right way to describe it. It flexes easy enough but it’s certainly not rubbery. I installed a clear filter between the pump and carb so I guess I’ll take it out and see what happens with the fuel when it dies. I don’t have a portable tank to try so that sucks.

Extra question... the kill switch has a crack in it that wasn’t there before and I’m wondering if it could have anything to do with it. How does that work? There’s 2 wires connected to it and I took it out and checked it for continuity. It’s open whether the switch is engaged or not. That doesn’t seem right so might be something wrong with it. Wouldn’t the engine not run at all if this was broken? Would it make it shut down only at wot? Weird.

 

[Zink357]

The way I understand the kill switch is when the lanyard is in place, the switch is open (or off) and not letting current thru and when the lanyard is pulled out then the switch is closed and it lets current thru straight to ground which shuts off all spark to the motor so in that theory, it should have absolutely nothing to do with my problem right? Either way, I am taking the switch out and seeing if it changes anything so we shall see.

 

[jerryjerry05]

Start the motor.
Stop the motor and unhook the wires from the KS
Try to start? Run?then it's an open circuit.
Paper clip between the wire ends.
Try to start, No? then it grounds the KS and kills the motor.

 

[Zink357]

I put a clear fuel filter in and it was getting gas to the carbs the whole time. Even when it died. Then after running it for awhile it just started working fine and I noticed a bunch of white gunk in the bottom of the fuel filter. It looks like mayonnaise. So I guess there’s something in the gas?? What is the white stuff?? Should I be draining the tank and starting over with fresh gas? This was the first time I’ve ever put 10% ethanol fuel in it. Is that the problem? Any ideas?

 

[Nordin]

Yes drain the whole fuel system (tank, fuel line, fuel pump with the built in screen filter).

You can try to run the engine from a portabel tank to check if the issue is gone.

I am in Sweden Europé and I Think we have much less ethanol in our fuel then in the US.
Think the white gunk have something to do with the ethanol part of the fuel.
Maybe it have something to do with if the is water in the fuel too.

 

[jerryjerry05]

White gunk in the filter?? That's a new one!!

Been using Ethanol fuel for years, it always seemed to separate in the hose from the tank
and cause hard starting.

If you use E then keep the tank full and use additives to stabilize the fuel.

Cleaning the tank, you can flush it through the sending unit hole.

REMEMBER THIS: an empty tank can blow up. Never use a vacuum or an electric/battery drill while working with the tank.

Guy in Md. used a portable drill to help remove a leaky tank.
Tank empty and flushed.
The spark from the drill=BOOM

 

[foodfisher]

Look out! My white gunk turned out to be a corroded aluminum tank. Had to cut out the deck to find out for sure. Replaced with plastic.

 

[foodfisher]

Added info. The previous owner/s were untidy. The drainage channel under the tank was clogged with cigarette packages, candy wrappers, fishing gear wrappers, leaves etc. that stuff held moisture to cause the corrosion from outside in.

 

[Zink357]

It has a plastic tank. I will try to upload a picture of the white stuff later, but from reading on other forums, it sounds like it is from an additive that some companies put in their ethanol fuel and it must be separating the water in the fuel or something. Like I said, it is running fine again now that the filter is keeping that **** out of the engine, but I think to be safe I should siphon the gas out and put a new filter on and some fresh fuel (non ethanol) in the tank. Probably clean the carbs too. Definitely not going back to that gas station for fuel ever again.

Jerry, how would I go about cleaning the tank or flushing it? I've never done that before. It is a built in tank and I have two access ports to it. One where the fuel comes into the tank as well as the vent tube and another where the fuel comes from the tank and heads to the engine. I imagine I could siphon it from there and then what do I use to flush it?

 

[jerryjerry05]

First thing I'd do: lift the front of the boat as far as you can, shifting any water in the tank to the rear.
Then use the hose and squeezie to siphon off a gallon or so.
Check what's in the gas you siphoned off.
Water, sludge, dirt?
Then I'd flush the tank.
I'd continue with the siphoning and after it's empty remove the sending unit and siphon off the rest.
The pickup tube won't get all the fuel.
I have an electric fuel pump that I use.
Make sure it's ok with the right (spark protected) switch.

After it's empty, inspect for gunk and crud left in the tank.

NO VACUUMS or Compressed air siphon tools.

Clean the tank and install the sending unit.

Some pickup tubes have a screen on the pickup end, remove the screen.
The next step will replace the screen.​

After all that, install a fuel/water separating filter between the tank and the squeezie.

 

[Zink357]

Here’s a picture of the filter with the white stuff in it. I’m at a loss as I’ve never seen anything like it. I cut open the filter and it feels like really weak silicone or something. So strange.

I drained and flushed the tank and there was definitely water water in the gas. Some of the gas that first came out hardly even had a fuel smell to it and then the majority after that seemed like good fuel and then the last gallon at the end had a more clear look to it. Certainly weird and idk what the issue was but hopefully it’s all good now. Not sure when I’ll get it on the water again but will update here.

 

[jerryjerry05]

Boat stove alcohol can help absorb some of the water in the tank.
Just make sure you add the right amount of oil to offset the alcohol.