86 Sea Ray 5.0 Mercruiser coil arcing

[XiViperI]

I just bought the boat, the first time out it blew the ignition coil.

I got towed in, went home and did a complete tune up changed plugs, wires, cap, rotor, sensor in distributor, and ignition coil. Next time I take it out, it runs fine for 20 minutes. I ancor off for an hour, then go to leave and it starts missing. I opened the hatch and discovered the ignition coil arcing to from the center coil wire terminal to the negative terminal on the top of the coil. The only thing I didn't change was the Thunderbolt ignition box mounted on the exhaust.

Should I buy a Mallory distrubitor kit and swap out ignitions?

What else could it be? A bad ground?

Its a 1986 5.0 Chevy 305 with thunderbolt IV ignition.

Any help would be appreciated.

Thanks!

 

[cr2k]

Re: 86 Sea Ray 5.0 Mercruiser

Re: 86 Sea Ray 5.0 Mercruiser

Just confirming the - (neg) coil terminal was the one going to the dist?

 

[XiViperI]

Re: 86 Sea Ray 5.0 Mercruiser

Re: 86 Sea Ray 5.0 Mercruiser

The coil is a standard round coil. It has two small posts one neg one pos then in the center it has the wire terminal going to distributor. Its arcing from the wire terminal to the negative post. It only happens once the motor is warmed up also if I push it into higher rpms while its arcing it will start arcing across the whole top of the coil pos, neg and wire terminal. Please help! I'm gonna put yet another coil on today but I don't think its gonna change anything.

 

[XiViperI]

Re: 86 Sea Ray 5.0 Mercruiser coil arcing

New coil did it.

Ran 8 hours yesterday no hiccups, finally get to enjoy the new boat!

I like all the info in this forum I will be back!

Next project is u joints and gimble bearing. They are a little noisy when turning.

Ed