wander into your local autoparts store...
Ask for an internally ballasted 12 volt coil. Spend no more than 25.00. If they demand an application, smile sweetly and say for an Atomic-4. When their eyes return to focus, say... "something from a mid '60' or 70's chevy"
Return to boat, coil in hand. Remove coil from A4, along with the ballast if so equipped ~(either a ceramic looking thingy about 3 inches long, or a curled like a telephone cord type of wire that attaches to the coil. feel free to cuss like a sailor at this point), replace ballast or wire with 12 guage stranded copper wire (oh, geez, tinned,crimped, superglued, varnished, cut by a virgin, marinized, marinated, frozen to -86.39 blah, blah, blah ~ tongue firmly in cheek) tighten the clamp and all nuts, and fire that mutha up. You'll be fine.
If you get a wild hair sideways, now might be a good time to replace the distributor cap and rotor too.
Standard interchange part numbers...
Borg Warner D152P
If you're feeling like Smoky Yunick Or Keith Black while replacing the cap & rotor, you can bribe one of your lady friends out of one of her paper nail files and run them thru the points a couple of times, just to clean them up.
We are not primarily on earth to see through one another, but to see one another through
Some people are like slinkies: not really good for anything... but you can't help laughing when you push them down the stairs