150 stalls at WOT...no obvious issues

[ab1]

1993 J150GLETR. Boat starts fine when launching, and generally runs pretty good. Bulb pumps firm, hold key in for 8 secs, fire it up, warm up, and go.

Lately I have had a few problems with stalling at WOT. If I keep it just under WOT, it does ok. But sometimes when I go to WOT, it will act like it is losing fuel and die. It either just dies flat with no other signs, or it will cut in and out and then die. If I'm quick, I can pump the hotfoot and get it to come back. Or, if I slow down to under WOT it smooths out and runs fine.

It has also stalled a few times at idle lately, but seems sporadic.

After it stalls, it is a bear to get restarted. The bulb is soft, but not flat. I generally just pump it back up firm and turn it over until it will eventually fire. Often it takes many tries to get it to fire. It helps to let it rest for a bit if it won't restart right away. Yesterday, I pulled the airbox off, let it cool, went back through the cold start procedure and it would fire. Seems if I push the key in like I was just launching it helps it to start.

No alarms, doesn't seem to be getting hot, VRO is hooked up and working, compression is good, spark is good (at least when I get it back to the garage). Thoughts?

 

[bigrockets]

Re: 150 stalls at WOT...no obvious issues

What is the tachometer reading at WOT? Sounds like a fuel delivery problem. You may want to look at the Secret File at the top of the forum and go through the fuel pump and fuel delivery tests. The stalling at idle could be a different problem such as clogged low speed jets but if the fuel pump is not delivering the engine will definitely die at WOT as the fuel level goes down. You also need the OEM shop manual. Don't waste your time with Seloc or the other aftermarket manuals. There is a fuel pump test proceedure in the shop manual. Maybe someone on the forum can help you with that.

 

[ab1]

Re: 150 stalls at WOT...no obvious issues

Tach at WOT is about 5500...I need to raise the motor a bit so I might gain some.

I've got the OEM manual and I'll read up on testing the fuel pump. Can these be rebuilt, or only replaced? I assume the problem would be on the fuel side and not the oil side...but honestly I've never been through one of these pumps before. I generally mark a line on the oil tank and monitor closely. Seems to drop at a reasonable rate.

 

[jonesg]

Re: 150 stalls at WOT...no obvious issues

3 simple troubleshooting steps.

1 Pump the bulb when it starts cutting out to test the pump at WOT.

2 Hit the choke, if it picks up the carbs are clogged.

3 A timing light will show if ignition is breaking up under load.





.

 

[Chris1956]

Re: 150 stalls at WOT...no obvious issues

Stalling at WOT is not a carb problem. If it runs for a few minutes and then dies, it is likely a fuel delivery problem. First see if the primer is sucked flat. If so clean the antisiphon valve on the fuel tank pickup, and the fuel tank vent.

If the primer is firm, see if pumping the primer bulb at WOT fixes it. Then look for air leaks in the fuel line and finally look to rebuild the vapor pump on the motor followed by the OMS pump.

 

[ab1]

Re: 150 stalls at WOT...no obvious issues

The bulb is not flat, but is soft after stalling. I thought this was normal...prime it firm to start, but once the fuel pump starts moving gas it just becomes a wider part of the hose and will naturally not be as firm. Correct? It's definitely not being sucked flat like it is developing a vacuum.

What are you able to rebuild on this motor pertaining to the fuel pump or OMS pump...I thought I read that you couldn't rebuild, only replace this pump, or that you could only rebuild the fuel side or vice versa.

1993 J150GLETR

 

[Chris1956]

Re: 150 stalls at WOT...no obvious issues

The bubl can be soft after the motor is running a bit. Check for airleaks in the fuel line from the bulb to the motor. Check any fiters, the main strainer or water seperators for air leaks as well. Will the motor run at WOT if you pump the primer?

The vapor pump should easily be rebuildable. The OMS Pump has a rebuild kit for the gasoline side. You might pick up a OEM service manual, since following a specific procedure is a good idea.

 

[archcycle]

Re: 150 stalls at WOT...no obvious issues

Could this be a stuck float in one or more carbs? Seems like if they weren't allowing you to refill reliably then you could just not have the fuel available for a long WOT run?