Failed Moyer Marine Coil

[Boat]

My intention is to not get into the big coil debate and etc. that follows someone asking about coils. I have had a coil from Moyer for 8 years. Flawless operation to date. I was doing some spring commissioning, plugs, oil, spring weights etc. engine idling and purring along at about 800 rpm. Nothing different from years past. all of a sudden the motor stops. just shut off. Checked all around, fuel etc. fuel pump all good. coil real hot but it fired right back up after about 10 minutes or so. a week later, same thing. I had a new moyer coil as a backup. installed that and hasnt done it since.

My main question is that i read the big coil thread and i think i have to much stuff attached to the coil. i have the EI, fuel pump, ignition. i have one extra on the negative side other than the EI that i didnt track down because of the rain.

What should be on the coil? where do i hook the extra things up to if not the coil?

[Al Schober]

I wouldn't be concerned about stuff attach to the + side of the coil - they just use it as a power source. Coil current (heat) depends on what is attached to the - side. Do a voltage check. Perhaps the regulator in your alternator is getting 'strange' and sending too much voltage to the coil?

[Surcouf]

Only time I had a hot coil shut down my engine was after engine overhaul: I had re-installed the coil closer to the exhaust, and there was too much radiant heat. Coil overheated during a rough seas motoring sequence. Installed additional heat wrap around the exhaust and a heat shield, and went through the remainer of the season without issue. Lesson: just be carefull with exhaust radiated heat

[Boat]

mine is in the standard spot back of the head. one failed coil in several years isnt bad i guess even if you do all the recomended proper things, will it eventually fail?

[joe_db]

Anything can break, including coils. I would not expect a coil with the correct resistance and supply voltage to be dying frequently, but after 8 years isn't horrible. Double check the supply voltage when you put the new one in.
The original coil that came with my original A4 lasted maybe 11-12 years or so.

[Boat]

what is everyone ideal supply voltage that i should be at? ill check mine and report back.

[Peter]

To avoid coil failure you want to limit the current in the primary to be less than 4 amps.

1) measure voltage at positive terminal of coil wrt ground
2) measure resistance of coil primary winding
3) if voltage/resistance is less than 4 all good
4) if greater than 4, add a ballast resistor to get it down to 4

Hope that helps,

Peter