Engine stalling in Four Winns Horizon RX 4.3L

[tertel]

Any advice would be greatly appreciated. I have a 1998 Four Winns Horizon RX with a 4.3L engine. The problem I'm having is that the engine sputters and stalls occasionally. It appears to happen most often when I'm attempting to pull either a tube or water skier. Just as the weight is engaged and the bow rises to try and start pulling the engine stalls. Once it stalls it will not start again until I pull off the fuel filter, top it off with fresh gas and then put it back on. Then I spray some ethanol in the carburator and it fires up and runs. It almost seems like I'm getting air in the gas line and then the fuel pump can't get its prime back(this is a guess, I do not really know what the problem is). Has anyone else had a similar experience and if so what was the solution?

[marshmat]

A few possibilities I can think of (our engine guys on here will surely come up with more and better suggestions):
- Carb jets not set properly for your boat and air conditions
- Fuel pump faulty
- Fuel filter badly clogged
- Leak on suction side of fuel system

[tertel]

Thanks for the response. I changed the fuel filter and it made no difference so thats probably not it. A couple of questions on your points:

1)Is their a way to check if the fuel pump is faulty?
2)Should the fuel filter always be full or is it OK that when I pull it off it is usually no where near full
3)How would I find/fix a leak on the suction side of the fuel system
4)I'm handy but not a carb expert. How hard would it be to adjust the carb jets as you described

[stonebreaker]

If the fuel filter isn't full, then you have some sort of leak in the fuel line. Start with the pickup tube in the tank, and work from there.

[tertel]

Thanks, I'll start checking there. A couple more comments and questions. This happens very infrequently(4-5 times all last summer). If it was a leak wouldn't it happen pretty regularly? It always seems to happen as I'm giving it a lot of throttle to accelerate quickly(like when I'm trying to get a skier up). Could the nose going up and the stern going down somehow be related to this problem.

Also, just for my education, would a leak cause the engine not start?

[stonebreaker]

It's hard to diagnose something online. The fact that you notice air in your fuel line indicates that there's a leak somewhere. It could be anything, something as simple as the pickup tube sucking air, or maybe a loose fitting, or maybe a tear in the fuel pump diaphram. You'll just have to methodically check your fuel line from beginning to end to find the leak.

[Ike]

Stonebreaker is right. What's happening from your discription, is the engine is sucking both air and fuel. So either your pump is not getting enough fuel (obstructions, clogs in the line, sediment in the fuel tank pickup screen) or there is an air leak somewhere in the system, and the only time it happens is when the engine is really under a heavy load and demanding lots of fuel.

A good marine mechanic could diagnose this pretty quickly but trying to do it online is iffy. I would start at the fuel pump and work my way back to the fuel tank. check every fitting. This could be something as small as a pinhole in a fuel line, which won't leak fuel because it is under negative pressure, but when your fuel pump is operating at it's max will suck air into the fuel line. A pressure test will find this. You might want to take it to a mechanic and have the system pressure tested. That will reveal a leak quicker than any other method. If nothing back to the tank, then pull the pickup tube and check the screen on the pickup. It may be clogged and starving the fuel line.

[Ike]

Whatever you do be damned carefull. This is gasoline you're dealing with and any spark can set off the vapors. So make sure everyhting is off, disconnected your batteries and make sure no one else is doing something stupid, like smoking. Don't laugh. I've seen it happen. And work in a well ventilated space.

[Beech2000]

Wonder if water is working its way up.

My 1986 four winns horizon 170 had this happen. It would sputter and eventually quit during skiing. Appears as if normal 40MPH cruises would offer the carb cleaner fuel and skiing (Low speed high torque) pulled the water from bottom of tank. (Go figure)

Took a while to figure out. I eventually pulled tank from floor and had it steam cleaned and pressure checked. Appears water had been entering in from vent from kids climbing back into boat wet. Once I adjusted position of vent no further problems. Just a thought.