Thunderbolt IV ignition module needed

[seadog brian]

Working on a 1994 350 magnum, Ser. # 0F131944. Ignition module has V8-24S on it, but not sure if it has not been changed in the past. What is the correct replacement part no., and where can I avoid paying $500 for one?
Thanks for the help in advance

 

[GA_Boater]

Ebay, CL or a boat junkyard for a used one after figuring out what you need. Owning a boat isn't cheap.

 

[Fun Times]

You are looking for Mercruiser part number 821125A1 which is TB4 Ignition Module due to your module is mounted to the exhaust manifold correct? You could also search V8-24 Mercruiser Thunderbolt Ignition module. You can still find this one both new and used.

http://www.iboats.com/MODULE-ASSY-IG...iew_id.1626971
http://www.iboats.com/350-MAG-ALPHA-...iew_id.1692130

 

[GA_Boater]

You saved $170 today. :smile:

Thanks Fun Times.

 

[alldodge]

Are you sure its bad? Have you gone thru the troubleshooting guide?

 

[seadog brian]

First, Thanks for the replies.
This module is mounted on the distributor. I have gone through the troubleshooting chart, but my problem is not spark/ no spark, but weak, yellow spark. Have changed sensor inside distributor, coil, plug wires, cap, rotor. Have taken shift interupter out of the circuit, along with tach. wire. Can't think of anything else. HELP!!

 

[FreeBeeTony]

I agree w/ AD............make sure it's bad before you spend that much $$$.

 

[alldodge]

First, Thanks for the replies.
This module is mounted on the distributor. I have gone through the troubleshooting chart, but my problem is not spark/ no spark, but weak, yellow spark. Have changed sensor inside distributor, coil, plug wires, cap, rotor. Have taken shift interupter out of the circuit, along with tach. wire. Can't think of anything else. HELP!!

The module has nothing to do with how strong the spark is, it's just the switch (so to speak) to innate the spark. You will find most statements say it should be bright blue. My opinion is the spark needs to ignite the fuel and what is being seen with a spark plug tester or by holding the wire/plug is just visual. What problems are you having which causes you to suspect spark?

 

[bman440440]

have you replaced the coil? most of the time I found that a weak spark was either from old/bad wires or coil and most of the time it was the coil

 

[seadog brian]

Coil has been replaced, and when I said module, I should have amplifier. Trigger/ sensor under cap has also been replaced.

 

[Bt Doctur]

Is this mounted to the port riser?

 

[seadog brian]

4bbl carb.
What #'s on the manifold mounted amplifier?

 

[FuelishBehavior]

Solve everything by ditching the TB IV which is pretty much now obsolete and the expensive replacement parts and get a Delco Voyager EST which is a whole new ignition system for the price of a new module. It is a direct replacement. Now when things break, and they always do, it's much cheaper to repair and you can get them off the shelf.

 

[NHGuy]

No don't buy a Voyager EST yet. Make sure yours is bad. That Delco has none of the smart features of a TB V. No knock sensing and smart timing advance. Why would you throw away something that's better til you are sure it's done?

 

[alldodge]

NH he has a TB-IV, no knock sensor

 

[NHGuy]

Gotcha, still might be usable. How is the battery strength? It needs a full charge to test for spark visually. How is the wiring and the wire ends? Are there good contacts where the wires attach to the coil and ignition components?

 

[achris]

.... It is a direct replacement. ....

No, it is not. Shift interrupt switch wiring needs to change, and getting it wrong is even more expensive.

Just get the TB-V module and enjoy the benefits of an upgrade, AND keeping the engine as close as possible to factory original, which makes fixing it in the future easier. Worst engines to work on are 'Frankensteins'. Don't know what part comes from where, or what other changes have been done to 'make it work'.... I send them away. Tell them to go find the orginal Mary Shelley....

Chris..........

 

[Rick Stephens]

When I had a failure I found it cheaper and more effective to replace with a EST Voyager. I still don't know whether it is module, coil or pickup that failed on the Thunderbolt IV, but a moot point as it wasn't worth starting down that road of replacing each part until you find the bad one. Silly way to test obsolete stuff when it costs in the hundreds.

 

[achris]

When I had a failure I found it cheaper and more effective to replace with a EST Voyager. I still don't know whether it is module, coil or pickup that failed on the Thunderbolt IV, but a moot point as it wasn't worth starting down that road of replacing each part until you find the bad one. Silly way to test obsolete stuff when it costs in the hundreds.

Don't need to 'shotgun' repair. There is a flowchart that will identify the failed part in a few minutes...

Chris........

 

[JustJason]

Another Vote for just changing it to an EST system. You can get an entire EST system for less than the cost of a TB4 module. Installing an EST system doesn't change the engine to a Frankenstein motor as long as the person doing the work is neat with their wiring. Later model engines all the EST system.