4.3LX Ignition Coil Thunderbolt IV Info

[boatingguy]

Anyone help with some basic info? I have a 1996 4.3LX with Thunderbolt IV ignition. To my knowledge everything is stock. The Mercruiser part number for the Ignition coil is 805570A2.

Does anyone know the resistance of this coil? Does it use the internal or external resistor? Any other info that is useful?

I went to a local marine parts house and they sold me a "Pertronix Flame Thrower" (part number BBB112006). It says on the box that it is a 1.5 Ohm. It also says that it is for v-8 engines and that a 3 Ohm is for 4 & 6 cylinder engines. Also it seems to imply that you would need some other distributor or ignition parts.

I am not willing to install this without really knowing if it is the correct coil. My gut says it is not, but I don't really have a comfort without a cross reference on the part number.

Any help appreciated.

Thanks,
Randy

 

[Don S]

Re: 4.3LX Ignition Coil Thunderbolt IV Info

Why are you replacing the coil?

 

[boatingguy]

Re: 4.3LX Ignition Coil Thunderbolt IV Info

Why are you replacing the coil?

Went to the boat on Sunday; would not start. Hooked up a timing light to see if I was getting fire to the plugs - nothing. Unplugged the coil and re-plugged. Engine started right up. Boated for 20 minutes; engine died suddenly. Played with plug on the coil pack again and the engine started up. 10 more minutes, engine dead again.

My assumption is that it is either coil pack or the coil wire to the distributor, so my plan was just to replace both and be done with it.

 

[achris]

Re: 4.3LX Ignition Coil Thunderbolt IV Info

Went to the boat on Sunday; would not start. Hooked up a timing light to see if I was getting fire to the plugs - nothing. Unplugged the coil and re-plugged. Engine started right up. Boated for 20 minutes; engine died suddenly. Played with plug on the coil pack again and the engine started up. 10 more minutes, engine dead again.

My assumption is that it is either coil pack or the coil wire to the distributor, so my plan was just to replace both and be done with it.

As this is a TB IV system and NOT a standard, garden variety Kettering ignition system, make no assumptions. Get the troubleshooting flow chart for the TB IV (available in the factory manual) and follow that. Just wiggling the connector does not indicate anything. You may replace the coil and connector, just to find that one of those is not the problem...

Chris.........

 

[Don S]

Re: 4.3LX Ignition Coil Thunderbolt IV Info

To check spark, remove the coil wire from the center of the distributor cap, hold about 1/2" from a good clean (unpainted) ground and crank the engine. You should get a bright bluish white spark that snaps across the gap easily.

Here is the troubleshooting chart for the Thunderbolt IV ignition.