95 sportjet 120 stalling

[Goodmanheelzfan]

Got this thing as a project, been sitting a while. Rebuilt carbs, replaced fuel lines and did the JB Weld repair on the wear ring and replaced the ride plate seal. Thing starts right up and gets on plane in seconds. Runs great for 20-30 minutes then dies and will not restart. Has fuel, spark and the compression is around 150 on all cylinders. Sits overnight and starts right back up. Any ideas? Checked thermostat and it's fine. Opened right at 130. I have the Clymer manual and the timing is at 30 btdc on full throttle when cranking. Rev limiter heating up or what should I check? Auto enricher closing in a couple minutes as well.

 

[jerryjerry05]

There is a sport jet forum.
The running for a while and then quitting.
Sounds like it's getting hot and shutting down.
Maybe a heat gun and check the temp on the motor?

Was it used in salt water?
When you removed the thermo? how much crud was on it?
Any build up behind it?

The pic shows a thermo from a running motor.
The motor spent it's entire life in salt water.
The cooling passages were about 60% full of gunk/ sand.

It didn't overheat???

 

[Goodmanheelzfan]

Sorry for posting in the wrong area. 1 owner boat never been in salt water. No crud and appears to be no blockage. I will get a temp reading. Where should I target (head) and what would be a normal temp? Assuming 130 to 140...

Thanks for the help!

 

[Redbarron%%]

At about 140 you would get a temp alarm so the temps should be that or less.
It could be heat related in the electronics.
I would get a spark tester and run it until it quit and see if you have a spark at that time.
I had a problem with the fuel pump on my 90 and it would run good for a while and then quit.
pumping the bulb would get it going again, but only at low power.

 

[Goodmanheelzfan]

Thanks again!

 

[Redbarron%%]

You might also check for water in the fuel.
I had a problem with condensate and crud in the 18 gallon tank in my Hobie Jet.
I installed an inline water separator / filter but I also ended up needing a new fuel pump kit.
The new kits have clear "plastic" check valves since the rubber ones were coming apart with the ethanol in the fuel.
I also installed an electric primer pump in case that new overhauled fuel pump decides to quit.
A little water in the fuel building up in the carbs will make one stop as well.
My guess is that either the electrics or fuel is failing.
A good induction timing light will let you see if there is spark getting to each plug when it quits.
I had one cylinder that would not fire at higher RPMS and this helped me find that.
Just clamp on each c
Cylinder's lead in turn.
A fuel pressure gauge in the line to the carbs is also a good idea.
I used one to check cooling pressure and then fuel pressure.
A good investment for troubleshooting.
As to the rev limiter killing the ignition if you remove the black and yellow wire (I think) that will remove it from the circuit.
Some are wired so that the lead is also from the kill on the key switch and if you don't reconnect it you can't kill the engine with the key.

When I determined that I had a problem on one cylinder of my 90 trigger coil I bought a new one, but also a wiring harness for a three cylinder with the CDMs and bought three modules for a 200 hp Mercury and replaced all of the banjo work switch boxes and junk.
The late model electronics are much more reliable than the older force parts and cheaper too.

 

[Goodmanheelzfan]

All good info. Thanks!

 

[Goodmanheelzfan]

To close this thread out the rev limiter was failing. When it got warm it would limit spark. Pulled yellow black wire and runs like a bat out of hell. New limiter installed and no more problems, yet... Engine was not overheating just getting to operating temp.