Mercruiser Thunderbolt IV Coil

[95yj]

Greetings, I have a 97 Merc 5.7L "new" longblock with a Thunderbolt V ignition with 60 hours on it that won't start. The spark is weak and the coil is out of specs from an ohm meter test per the specs in the Merc manual. The only place to get a coil for a boat on this island is from the NAPA dealer. NAPA shows part number 185438 (same part as Sierra) which lists the Thunderbolt as a direct application but they don't stock this part. NAPA also shows the Echlin IC88 as a direct replacement for the 185438. NAPA's web site doesn't show any marine application for the IC88. All they show are a bunch of foreign autos from the 70's, 80's and 90's.

Does anyone know if this coil will work with the Thunderbolt ignition?

 

[achris]

Re: Mercruiser Thunderbolt IV Coil

Thunderbolt IV and V use the same coil. I used a non-resistor coil (Bosch GT40) in place on my old TB-IV engine (1994 4.3LX) for many years.

HTH.

Chris..........

 

[95yj]

Re: Mercruiser Thunderbolt IV Coil

The IC88 coil has no information in the specs. Other than if the specs say non resistor or for electronic ignitions, is there any way to certain that a coil is a non resistor?

 

[Bondo]

Re: Mercruiser Thunderbolt IV Coil

The IC88 coil has no information in the specs. Other than if the specs say non resistor or for electronic ignitions, is there any way to certain that a coil is a non resistor?

Ayuh,... A resistored coil, will show Less than 12v on the (-) side, when 12v is applied to the (+) terminal...

If it passes through the 12v, it ain't a resistored coil...

 

[95yj]

Re: Mercruiser Thunderbolt IV Coil

Ayuh,... A resistored coil, will show Less than 12v on the (-) side, when 12v is applied to the (+) terminal...

If it passes through the 12v, it ain't a resistored coil...

Thanks Bondo, the problem is that I'm sure the NAPA dealer won't allow me to hook it up to a battery to test it before I purchase it. I can probably put an ohm meter on it though. The stock coil is supposed to show .6 - .8 ohms across the primary. I was wondering if anyone knew what resistance a coil with a built in resistor would read. Although I can probably assume that anything over 1 ohm would be no good. I think that 1.8 ohms will drop from 12vdc to 9vdc.

 

[VoIPGuru]

For anyone else that finds this posting, the Napa coil worked fine for me. NAPA part num ECH IC88 worked for a Meecruiser 5.0 Thunderbolt IV setup.