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4.3L Thunderbolt V Ignition

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tsinks23

New member
Hello all, looking for a little help. I am in need of a ICM part number
  • 861251T1 ICM MODULE
For a 04 4.3L Merc. I was hoping to find a used one for cheaper before I go out and order a new one for 600$

If that is not the case does anyone know of an upgraded system that would cost about the same amount and still be USCG approved? If I’m already spending the money I’d rather upgrade. Thanks!
 
tsinks23 said:
Hello all, looking for a little help. I am in need of a ICM part number
  • 861251T1 ICM MODULE
For a 04 4.3L Merc. I was hoping to find a used one for cheaper before I go out and order a new one for 600$

If that is not the case does anyone know of an upgraded system that would cost about the same amount and still be USCG approved? If I’m already spending the money I’d rather upgrade. Thanks!
Click to expand...
Usually you can find them on eBay used, but as more icms have become NLA that is getting harder to find. Green Bay prop used to list a lot of used parts not sure if they can help.

If all else fails a delco est is a common replacement and is relatively drop in with minor wiring changes. The original delco is est is a OEM quality system, used on some VP and mercruiser engines from the factory. There are cheap knock offs out there that may or may not be of similar quality. Michigan Motorz sells est systems
 
If it were me,
I would look for any version of the thunderbolt ICM for a V6, IV or V early version.
TB IV did not have the mean best timing or the knock sensor and module so some minor wiring changes would need to be made but it WILL work.

I believe the early TB V modules also did not have the knock system but were a smaller package design and also would require some rewiring but will also WORK.

Actually V8 TB V with knock will also work. The difference is when its fully advances the timing and total advance.

The Module doesnt care how many cylinders a engine has.
The only real difference is the timing, when full advance comes in and total advance and connector design.
 
kghost said:
If it were me,
I would look for any version of the thunderbolt ICM for a V6, IV or V early version.
TB IV did not have the mean best timing or the knock sensor and module so some minor wiring changes would need to be made but it WILL work.

I believe the early TB V modules also did not have the knock system but were a smaller package design and also would require some rewiring but will also WORK.

Actually V8 TB V with knock will also work. The difference is when its fully advances the timing and total advance.

The Module doesnt care how many cylinders a engine has.
The only real difference is the timing, when full advance comes in and total advance and connector design.
Click to expand...
I believe the TB V knock or no knock sensor is more determined by what engine it is on. Seems like even with the latest TBV modules the base 4.3 and 5.0 2 bbls I have never seen with a knock module. Seems like more so they come on higher hp 5.7s

I am pissed at MErc for how many TBV modules are now NLA, which dries up the used modules available. When I did my repower back in 2015-16 I was able to find them all the time for $200 or so on ebay not the case anymore.

You are correct that with a little rewiring and the right connectors any module will work. I ran my 5.0 with 4.3 and 5.7 modules to test it on a stand no issue.

really sucks that they are NLA or $$$$ as it is such a good system. Have had zero issues or need to rest my timing in 11 seasons now, just preventative cap and rotor and plug changes every 3-5 years
 
Dieter said:
I believe the TB V knock or no knock sensor is more determined by what engine it is on. Seems like even with the latest TBV modules the base 4.3 and 5.0 2 bbls I have never seen with a knock module. Seems like more so they come on higher hp 5.7s

I am pissed at MErc for how many TBV modules are now NLA, which dries up the used modules available. When I did my repower back in 2015-16 I was able to find them all the time for $200 or so on ebay not the case anymore.

You are correct that with a little rewiring and the right connectors any module will work. I ran my 5.0 with 4.3 and 5.7 modules to test it on a stand no issue.

really sucks that they are NLA or $$$$ as it is such a good system. Have had zero issues or need to rest my timing in 11 seasons now, just preventative cap and rotor and plug changes every 3-5 years
Click to expand...
Dieter,
Manual 18 which shows carbed TB V ignitions clearly shows a second KNOCK control module used for the V6.
The next V6 manual is 25 but only speaks to the knock module but has NO images of the ICM or Knock module (Poorly written manual for TB V)




This past spring My friend (ONLY ONE....LOL) bought a 26 ft 454 mag Bravo 1, go fast boat. He purchased it As Is for a good price so he brought it to me.
Engine would not start.
I went thru the TB V trouble shooting procedure and the ICM was the cause. This was a piggy backed two module piggy backed ON the distributor.

I have a couple big block TB IV small package ICM's so I rigged one up and engine fired right off.

I went on Ebay and found NOS ICM for a his model/year 454 mag $500.00. I offered to sell my older TB IV and wire it up and he went with OEM and payed the $$$. Of course it worked and boat has been running great all summer.

Point is, The original module for your V6 lasted what? 20 years +.
Spend the $500/$600 or so and it should go another 20 + years.

If you update the entire ignition system to the EST for what $1000.00 + and the need to do rewiring and if you cannot do this yourself add another several hundred dollars for labor and misc parts.........

Your math doesn't make sense...........
 
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