After ripping it up I ended up getting pulled over by the coast guard for an inspection and they had me turn off the boat. 10 minutes go by and I get the all clear, I go to start it and it just cranks and cranks and doesn't fire. The coast guard mechanic came aboard and suspects it's the battery. I get towed in, grab my multimeter, check the voltage and it's about 12.3-12.4. I try cranking again and it's just not catching. I start thinking spark and check the coil. On the positive side I'm only seeing 11.3V. I notice clear oil leaking from the tower and figure I fried the ignition coil.

I ordered and installed a brand new coil (leaking is not a good sign) and it's still giving me trouble. No spark/weak spark.

Is 11.3V on the + side of the ignition coil too low? I've got 12.4 at the starter slave solenoid if that helps. Does it take 12.0 to fire properly?

Any help is appreciated

- Scott

Hey Scott I'm assuming your talking about BBC 454 carbed engine? Little more on the engine would be helpful however if you have enough voltage to crank engine over then you'd certainly have enough to start it. You need to check for spark and fuel. Thunderbolt ignition? Did the CG poke around in your bilge?

Sorry. Yes, it's for my carbed 89 454 Mag. It has the thunderbolt IV ignition.

They only started poking around once it wouldn't start. I only had some hand tools on me and we couldn't do much on the water. The CG mechanic did note that the positive battery terminal was hot.

Nothing else was touched. It would always start, especially this year after putting in a new starter and solenoid, and now with a new ignition coil.

The only thing I'm concerned is the 11.3V, as every other thread on the topic has people seeing 12V at the + side of coil

Any mice been been chewing on wires in places you can't see. You should have the same voltage within reason as you do at the battery. I guess what I would do is check the voltage to see what it drops to while cranking engine. Other thing you could do is run jumper wire from you starter switch to your coil and repeat voltage test. Is your back of your dash panel easily accessible?

Pull a plug and check for spark and make sure you have no fuel issues. Will be interesting if it makes any difference to get the same voltage at the coil. Also make sure your TB module is plugged in all the way and look for any grounds that may have come lose.

Already pulled a plug. Since the boat is dry docked at the marina and I was solo, I recorded a plug.

https://youtu.be/KAuDm5Bu6Kg

I don't think you can see it on the upload but the raw video there is a tiny tiny spark once i stop holding the key to start.

And yes, I can get behind the dash pretty easily. Is there something I should check behind there?

Do you even have the base of the plug grounded to the block in that video? Assume it is plugged into a wire?

Im dumb. I didn't ground it. I was solo and getting frustrated and wasnt thinking. I'll try it again and see if anything changes.

So it has not yet started since getting pulled over? Got towed in?
What does the inside of the distributor look like?