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5.0 litre merc coil issues

H

Hounder

New member
My coil burned out. I replaced with another and had good success. It too quit working four hours later. Could the problem be the resister. If so would it be an inline wire resister or of the ceramic type. I cannot locate this. Where can I find out what type of resister is required as I bought another coil and it is stamped resister required with this coil.
 
Point ignition needs a external resister coil or a ballast resistor

A thunderbolt electronic ignition needs a internally resister coil
 
My boat is a 1994 bayliner 2450. The replacement coil ( HEI ) I got states on the side, use with external resistor. I will check to see if it a points ignition or the Thunderbolt. Do the resistors usually burn out or just the coil.
 
You have the wrong coil that is why it is frying........... without the built in resistance the coil is getting too hot.

The thunderbolt ignition systems DONT have any resistance wire or ballast resistor..........That is why the coil must be internally resistored.

The coil you purchased is used on a old point ignition and the ignition had either a resistance wire (~2 Ohms and ~ 3 feet long in the wiring harness) attached to the + of the coil or a ballast resister (~2 ohms) between the power (purple wire) and the + on the coil. This reduces the current flow thru the coil.

Why they didn't just make a coil to withstand system current I don't know.........

Get one that is internal resister at any automotive parts store as it does not have to be one from a marine store. It make no difference what brand as long as it has the internal resister.

Marine and auto coils of that style are all the same in design (auto vs marine)

Your ignition, if mercruiser stock, is called Thunderbolt V and is HEI in design but not called HEI. (High Energy Ignition)

Older GM automotive HEI ignitions used a on distributor cap coil design..........That was the original HEI gm ignition.
 
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Thank you , you have answered the question which I had trouble from other mechanics that could not give me. I will exchange for the internal resister coil. It is people like you that make this world a better place.:)
 
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