This is probably a dumb question with a simple solution, but anyway here it goes.  I have a 74 model 43' Nautaline, twin 302's.  Last year one engine got to where it would run only if the key was held on, or a wire was ran from the coil to the battery, the boat was removed from the water for some repair, and now the other engine is doing the same thing.  Like I said, they run fine, as long as you hold the key on, or run the jumper wire.  Where would I start to look to fix this problem.  Also, the engines are of the same vintage as the boat.  Thanks in advance. 

Sounds like a simple worn ignition switch. A cheap fix to swap out and see.

I've seen a bad ballast resistor cause these same symptoms.

It may be the ignition switches, I kind of doubted both going bad at nearly the same time, but stranger things have happened.  I may change one just to see, if this isn't it, what is a ballast resistor?  Thanks again

It basically reduces the voltage to the coil after the engine starts to reduce wear on ignition parts. Not all manufacturers used them, though and I'm not familiar with those Fords. Chrysler and GM used them. Judge could very well be right about the ignition switches. You should definately start with the simplist thing. Just check if you have 12 volts out of the run side of the switch. You already know you have it out of the crank side. If you do do, check for 12 volts at the coil and while your at it, look for a ceramic block with two wire coming out of it mounted near the coil or distributor. That's a ballast resistor and they're sort of fragile. Hopefully, someone more knowledgable with your set-up, like OHB, will chime in and let you know if you even have them.

Switches are the most common cause of this problem. If you have plugin ignition harnesses take them apart and spray them good. OLD HOUSEBOATER39112.3776157407