Bad coil?

Linda,

This is a common symptom with multiple possible fixes. I have experienced it myself. Some always say check the antisiphon valve on the gas tank, but I, personally never believed that to be the situation when it is fine when cool, but not fine when hot. I think an anti siphon valve problem would not be time or temp dependent. other possibility: As you already came up with, coil. Yes they can fail when hot and be ok upon cooling down. Best way to check this is get a new coil, but not install it. Take your lake cruise again, and when it happens, then swap the coil. If you are good to go, then you know you have isolated and cured the problem. In my case it was a bad cap, but I think the crab (flat) caps are more susceptible to mild deformation and hence, bad contacts when hot (as told to me by a supplier.) A standard vertical connection cap may not have that issue. Best bet, try the coil and if that doesn't work, let the diagnosing resume.

Was an electronic conversion installed to replace the points??

Good to know, got my info from the site here somewhere along the way. Do you have any idea what makes them fail?

gun-driver wrote: Was an electronic conversion installed to replace the points??

No.. it has points. and condenser rotor as well... Old shcoll stuff I guess..

I'm wondering if maybe oil filled coils, laying on their side, are possibly a little more sensitive to seeing a full 12 volts?

If I understand correctly, both the old points distributors and the newer Mallory electronic dizzys use a ballast resister.

Somewhere in between there were Prestolite OEM Electronics like mine that don't use the resister.

But, there were also the electronic conversion kits. Which, I believe called for full, un-resisted (no ballast resister) voltage. So, then the ballast resister is taken out of the loop.

Now, I believe the resister is mainly there to protect the dizzy. But, the coil is also seeing lower voltage in a ballast resisted setup.
So, a coil is going along happy seeing, what 8-10 volts?, for years, then all of sudden, wham! 12 volts after an electronic conversion.

Many threads talk about ignition wiring, but this one just came up http://www.correctcraftfan.com/forum/forum_posts.asp?TID=29920&title=pro-tec-ignition-conversion-on-58-pro-boss

flooding carb?

gun-driver wrote: Bri892001 wrote: So, a coil is going along happy seeing, what 8-10 volts?, for years, then all of sudden, wham! 12 volts after an electronic conversion. If you notice in the drawing the distributor gets the 12v it needs from the in side of the resistor but the coil is still getting its power through the resister.

True, but that's a drawing of wiring for a newer Mallory.

I believe the older electronic conversions, bypassed the resister, therefore delivering a full 12 volts to the coil after conversion, like this:

How you wire your EI conversion depends on if you have a resistor type coil or not.
If you have a resistor coil you can bypass the ballast resistor, if you do not have a resistor type coil you still need to run through the ballast resistor.

This is all neither here nor there because the OP said she has points. I would check to see if the ballast resistor is bad and over heating the coil.

Hey there Big Daddy (and Mama too) hope to see you guys this summer.

That coil will eventually leave you stranded.

Can anyone provide me with some part nos.? Are these coils the same as those for street use on older cars such as Mustang? Napa sells one, part no. IC10SB,$23.50. So is this the correct coil. Don't know if my engine has been converted as suggested above. I know I have points. Will the Epoxy filled coil work either way? If so I would just go for that. Trying to buy one today before weekend. Nothing like waiting til last minute.

ny_nautique wrote: This is the standard coil for your engine.

Yes I know that but trying to cross reference locally.

Unless you know specific part numbers I've learned from experience to order from SKIDIM, Whitelake, N3 or go to a PCM dealer, Nautique or a long time Supra dealer. Local parts house is usually a crap shoot much beyond oil and filters. Prestolite cap shouldnt be hard to find, don't buy wires unless they're for a 351 marine engine, cars use shorter wires.

Thanks so much gun-driver. For me the coil on my boat is the one without the resister so I found out after I had bought the one you show here. I did not have my old one in hand and when I got to the boat to swap the new w old, the coil on it clearly said external resister not needed. So off to NAPA I went to swap coils. Not sure if it is why, but my boat has been converted to Pertronix, which I was not aware of. Anyhow, new coil or not, it did not fix the misfire. Next week I will pup the tuneup parts. How about the plugs?

Plugs are autolight #24, buy them anywhere. I was able to make 80's vintage Ford F150 351 plug wires work. I bought NAPA gold version.