1985 Ski Nautique engine stalling only after pulling tubers

[TRON]

Hey boys! I got a 1985 Nautique 2001. The boat runs perfectly fine as long as it takes breaks. However, whenever my family goes tubing for a solid hour or so the engine will eventually not fire up. Something is clearly overheating and causing the engine to not fire up after long pulls with tubers. The water pump is working and engine temps are good. I don’t think it’s mechanical problem. Could it be vapor lock or something electrical? Any insight would be greatly appreciated. We do have the wrong size gas cap. If it’s not air tight would that cause a problem after the engine running for a long time? Cause again the boat runs like a champ if it’s not beat on taking tubers out for over an hour

[hal2814]

Gas cap will just keep water out. What ignition are you running? That’s the first place I would go. Your boat came from the factory with points. If it’s still running points, that’s the first place to start. Check the contacts and set the dwell. Also check your condenser. If you or a previous owner did an electronic conversion it’s possible they wired it incorrectly. A lot of the modules need full voltage but the coils ran through a ballast resistor. If that’s the case they’ll usually run fine until the engine heats up. Then they’ll be hard to start. Vapor lock is possible but unlikely. If ignition checks out I’d take a look at the anti-siphon valve.

[TRON]

Yes it was changed to the electronic conversion. Let me know if I’m right here. So if you have the e conversion you should bypass the resistor? The coil is oil based and horizontal to the engine. Thoughts?

[hal2814]

It depends on the EI unit and the specific coil. Typically the ignition bypasses the resistor but the coil does not so you have to run a separate wire to the ignition unit instead of sharing a wire like you do with points. Alternatively, I’ve seen setups where the coil has also been changed so that it doesn’t require a resistor. In that case you bypass the resistor entirely and still share a wire. If you try the latter with a coil that needs a resistor it’ll work for a while but will eventually you’ll get hot start issues and lose the coil.

To throw a final wrinkle in there, EI units require a ground. Points don’t. You may want to check that the EI unit is properly grounded. I grounded mine to the alternator’s ground wire. I’ve seen people incorrectly ground an EI conversion and have issues due to that.

[TRON]

Let me find out the model numbers for the coil and EI conversion kit. And we go from there. Thank you for all the help thus far

[TRON]

So the EI conversion kit is a Pertronix 1581-82 (LOT#20 AJ-NV5M)
The Coil is a Pertronix flame thrower oil filled.

Whether the resistor is used or not to drop voltage. What is a good combination ignition coil and EI conversion kit that will not fail once
these 351w engines get hot? Seems Pertronix is not the best quality. What do you recommend?

[hal2814]

I’m not the best person to ask. I had more problems than just the points. My springs were worn and there was an actual chunk missing out of the timing gear so I ended up installing a new Mallory distributor that came with EI. Nautiqueparts sells a kit with the wiring, ballast resistor, and coil, but it’s a lot more expensive than it used to be. I do know there are multiple Flamethrower coils and they all need different resistance fed to them.

[functionoverfashion]

In my opinion, you cannot beat a full-electronic distributor as opposed to EI conversion kits when it comes to simple reliability. Points work great, when they work, and they're cheap and pretty easy to work with. But they can be finicky, and do require regular replacement. I have points ignition on my old truck and it's fine, however, I'd put an electronic distributor in, if it was a boat.