1986 Supra comp dies. Need help.

[TheBaldman]

I have a 1986 Supra comp with a freshly built 351 PCM motor. The motor has run great in the past, but randomly wont start. When I put the boat in the water, it starts up perfectly. After I leave the dock and travel at a good cruising speed (approx 30-35 mph) for 4 or 5 minutes, the motor dies. When you try to restart the engine, the motor will turn over, but will not start. I did not have my spark tester tool with me, but I did spray a little starting fluid into the carb, but still just cranked. After an hour of floating, the motor started and ran fine. I headed straight for the dock at this point. The motor is equipped with a Dura-Spark ignition box (converted from points) and has new plugs, wires, coil (external resistor style with no resistor). I would like to enjoy my boat for more than 5 minutes each time I put it in the water so any help is appreciated.

[Longhorn21]

You might want to check fuel filter or fuel pump. Take it to the lake and run it and take the spark arrestor off and look down the carb when it dies cause it sounds like your not getting fuel. It could also be your float needles sticking. Just take off your float bowl and clean inside with carb cleaner.

[TheBaldman]

I am think that is something in the ignition system is getting hot and shutting down. I think if I had spark, the starting fluid would have sparked.

[Longhorn21]

I wouldn't think it's your ignition system cause you posted that you had a new ignition, wires, and cap. Pull a spark plug with the wires on it and crank it up if it gets a spark then I would see if your getting fuel.

[SUPRALUVIN]

Could be a bad ignition coil...they can fail when hot. Also could be dirty or corroded points. Check for spark at ignition coil....if nothing there could be your points not opening up.When your points open it takes the ground away from the coil causing spark.

[JAKE HIGDON]

change your coil man i got an 85 comp that done the same thing! i also learned something new while trying to figure out what was wrong with it. i was getting rust in my carb from the water seperater mounted in the front left corner of the engine compartment . guy told me to put a clear external fuel filter in the gas line close to the carb and tape a magnet around it. the rust that gets through the filter will get stopped by the magnet!