Thunderbolt V vs 350 Mag Stern Drive Ignition Module?

tank1949

Ensign
Joined
Apr 4, 2013
Messages
951
I Purchased boat a couple years back and have taken too long to restore it. Way too long... But, all is almost complete. Former owner indicated MC V8s had Thunderbolt V ignition systems with knock sensors. While motors were on stands, I noticed that "350 Mag Stern Drive" labels were on both distributor modules, including knock sensors. However, my manual indicates that these modules are for EFIs. My motors both have 4 barrel carbs. During sea trial, these worked great. I suspect former owner mixed and match available parts which would work OK, or should I have an ignition module specifically labeled "Thunderbolt V?" Not familiar with this specific module...
 

alldodge

Supreme Mariner
Joined
Mar 8, 2009
Messages
31,223
The TBV should have a number listing how many degrees advance it provides (22 or 24). The TBV will work the same for an EFI or carb motor. Does the module have a part number listed?
 

tank1949

Ensign
Joined
Apr 4, 2013
Messages
951
The TBV should have a number listing how many degrees advance it provides (22 or 24). The TBV will work the same for an EFI or carb motor. Does the module have a part number listed?

Yeah, but I am not able to access right now. As soon as I get back from other duties, I will supply. I would have thought "Thunderbolt V" would have been labeled somewhere on distributor or module. Only the "Mag 350..." THX
 

alldodge

Supreme Mariner
Joined
Mar 8, 2009
Messages
31,223
Yes, TB4 to TB5 will work, just need a couple more wires. Most when a TB takes a puke they replace with Delco EST
 

tank1949

Ensign
Joined
Apr 4, 2013
Messages
951
The TBV should have a number listing how many degrees advance it provides (22 or 24). The TBV will work the same for an EFI or carb motor. Does the module have a part number listed?

Attached is photo. Only number that is easily seen is 806957-2 that is on both modules on both distributors/motors.
 

Attachments

  • photo323050.jpg
    photo323050.jpg
    973.4 KB · Views: 0

alldodge

Supreme Mariner
Joined
Mar 8, 2009
Messages
31,223
That is for the 5.7 as shown and new number is 807264T4 and should be 24 degrees total advance. Carbs where set at 10 and EFI set at 8 BTDC
 

tank1949

Ensign
Joined
Apr 4, 2013
Messages
951
That is for the 5.7 as shown and new number is 807264T4 and should be 24 degrees total advance. Carbs where set at 10 and EFI set at 8 BTDC

It will advance 24 degree total or 24 more degrees or 34 degrees(10 +24)? So I disconnect knock sensor and set timing at 10 degrees advance instead of 8 degrees advanced? Hum....I would have thought the opposite for carbed motors. I would have also thought MC would have had TB v or similar on label or maybe former owner didn't have access to these modules and used what he had access to. THX!
 

tank1949

Ensign
Joined
Apr 4, 2013
Messages
951
That is a Thunderbolt V module for a 350MAG engine, with knock sensor. Have you read my article on the Thunderbolt ignition system? (Here it is if you haven't -> http://forums.iboats.com/forum/engi...-mercruiser-thunderbolt-ignition-systems-work) That should clear you any misunderstandings you have of the system.

Chris......

Excellent information but I didn't see anything on "350 mag..." So, the "350 mag..." actually referred to motor and by default was a TBV ignition system? THX
 

achris

Moderator
Staff member
Joined
May 19, 2004
Messages
24,848
Ok. Thunderbolt is the trade name for Mercury's ignition systems. The 'original' Thunderbolt was on the inline outboards. In 1984 Merc put Thunderbolt (series) IV on the Chevy block stern drives and inboards, then in 1996, released (and fitted) Thunderbolt V series. Each TB module (be it IV or V) has the timing curve of the designated engine programed in.

The designations for TB-IV was the engine and the maximum advance (of the module), sort of. These were all the TB-IV modules fitted to the Mercruiser engines. That's between 1984 and 1996.
V6-14
V8-20
V8-20R
V8-22
V8-22A
V8-24
V8-24S

Which module went on which engine (and the actual timing curve) can be found in service bulletin 95-11 (easy to find online)

The TB-IV module for a 350MAG was the V8-24S, which also went into a whole bunch of other engines, that's why there isn't engine designations on the TB-IV modules, just one of the codes above.

In 1996 with the advent of TB-V and an adaptive curve, these codes no longer applied, so either part numbers or actual engine designations started to be used.

That's why on your module there is a part number and the engine designation. No, there's no "Thunderbolt V" written on it, that's implied by the module itself. It's a 'Thunderbolt V' module....

Hope that helps...

Chris........
 

tank1949

Ensign
Joined
Apr 4, 2013
Messages
951
Ok. Thunderbolt is the trade name for Mercury's ignition systems. The 'original' Thunderbolt was on the inline outboards. In 1984 Merc put Thunderbolt (series) IV on the Chevy block stern drives and inboards, then in 1996, released (and fitted) Thunderbolt V series. Each TB module (be it IV or V) has the timing curve of the designated engine programed in.

The designations for TB-IV was the engine and the maximum advance (of the module), sort of. These were all the TB-IV modules fitted to the Mercruiser engines. That's between 1984 and 1996.
V6-14
V8-20
V8-20R
V8-22
V8-22A
V8-24
V8-24S

Which module went on which engine (and the actual timing curve) can be found in service bulletin 95-11 (easy to find online)

The TB-IV module for a 350MAG was the V8-24S, which also went into a whole bunch of other engines, that's why there isn't engine designations on the TB-IV modules, just one of the codes above.

In 1996 with the advent of TB-V and an adaptive curve, these codes no longer applied, so either part numbers or actual engine designations started to be used.

That's why on your module there is a part number and the engine designation. No, there's no "Thunderbolt V" written on it, that's implied by the module itself. It's a 'Thunderbolt V' module....

Hope that helps...

Chris........

Very much! Thanks!!!!
 
Top