72 Johnson 125HP dies after 90 minutes

[LOSTBOATER72]

HELP!!!
Recently I took out my 72 Glastron with a V-4 1972 Johnson 125HP and it started sluggish as I had not taken it out in about 6-8 months. It ran great for about 90 minutes and then at full throttle it just died. It would turn the flywheel fine but would not start for about 45-60 minutes. After this time I started the engine and slowly cruised back to the dock and called it a day as I was baffled on what the issue was. The next day I got bold and took it out again, exact same scenario. Ran great for apx 90 minutes and just plain died at high speed. This time we floated to the nearest dock and pulled it in. Any suggestions? This is a completely rebuilt, new fuel line, new bulb for primer, new inline fuel filter, pretty much all new/rebuilt motor. new optima battery. I am lost. Thanks for any help anyone can provide. One note, there is a mist coming from the back of the engine as far as water cooling goes so I am pretty sure overheating is not it.

Thanks!
LostBoater72

 

[tashasdaddy]

Re: 72 Johnson 125HP dies after 90 minutes

did you check spark on all 4 cylinders, right after it shut down?

 

[LOSTBOATER72]

Re: 72 Johnson 125HP dies after 90 minutes

No I did not. Do you think that might be the issue? I do not see why it would have spark for 90 minutes then just stop? It has a new powerpack as of about 2 years ago with very few hours on it.

Thanks for your help!
LostBoater72

 

[R.Johnson]

Re: 72 Johnson 125HP dies after 90 minutes

I think the 90 minutes is just a coincidence. If 90 minutes were a factor, shut the engine off at 85 minutes, and start over. Kidding aside, I hade an engine like yours do that to me once. The problem was the wire between the ignition sensor, and the power pak had broken under the insulation. Disconnect these wires at the disconnect down from the stator. Hook up an ohm meter, and pull on the wires where they make the bend coming from the stator.