No Spark – 1998 MerCruiser 5.7L Thunderbolt V Ignition

[Marko_f1]

Hey Everyone,

I’ve been restoring my 1994 Bayliner 2452 for the last two years (new transom, new stringers, new fuel tank etc) and my mechanic finished his part this week. He rebuilt the Alpha One Gen 2 outdrive and swapped my old 1994 5.0 MerCruiser (1,800HRS on it) for a 1998 5.7 MerCruiser with Thunderbolt V ignition which has just over 400 hours.


Everything ran fine at first, but it wouldn’t shift into neutral. My mechanic realized he had set it up like a Bravo system and forgot the shift-interrupt switch that’s required for Alpha drives. He gave me my old switch and told me to tap the white/green wire from the switch into the same color wire going from the distributor to the harness, and ground the black wire from the switch - I did that and shifting worked perfectly fine.

Then, after about a 45-minute cruise, right as I backed off the throttle (before even hitting neutral), the engine shut off instantly and hasn’t fired since and the problem is no spark.

What I’ve checked and done so far:

• Engine is getting no spark.
• Replaced the pickup coil/module inside the distributor with the new fully-enclosed style (no change).
• Verified coil positive (purple wire) has 12 V with key on.
• Verified ground to the ICM (black wire).
• Tried bypassing the knock module – no change.
• Coil seems to be working (I swapped with my old one and no change).
• Tach started bouncing up and down while the actual RPM were steady (at idle the tach would go up to 3K RPM and back down to 1K)
• Disconnected the main engine harness, jumped 12 V directly from battery to coil +, jumped the starter solenoid studs – still no spark.
• Test light between coil + and coil – dims but does not flicker while cranking although it’s got an incandescent bulb and thus may not pick up the quick pulses an LED test light would.

The ICM (riser-mounted box) has “5.7 Bravo” printed on the back as it came from a boat with a Bravo outdrive but it’s now paired with my Alpha outdrive, so I’m wondering:

• Could using the Alpha shift-interrupt switch with a “Bravo” ICM have damaged it?
• Or does that not actually matter as long as the shift interrupt switch was installed?

Hopefully somebody on here is super familiar with the T-Bolt 5 ignition system or had a similar issue and can chime in as I feel like I’m hitting a dead end here except for ordering a new ICM. Thanks in advance for your help!!

 

[alldodge]

Could be Tach is shorting out or interruptor switch is staying engaged

Disconnect the Tach and the interruptor switch

If after that there is still no spark run thru this test

 

[Scott06]

Hey Everyone,

I’ve been restoring my 1994 Bayliner 2452 for the last two years (new transom, new stringers, new fuel tank etc) and my mechanic finished his part this week. He rebuilt the Alpha One Gen 2 outdrive and swapped my old 1994 5.0 MerCruiser (1,800HRS on it) for a 1998 5.7 MerCruiser with Thunderbolt V ignition which has just over 400 hours.


Everything ran fine at first, but it wouldn’t shift into neutral. My mechanic realized he had set it up like a Bravo system and forgot the shift-interrupt switch that’s required for Alpha drives. He gave me my old switch and told me to tap the white/green wire from the switch into the same color wire going from the distributor to the harness, and ground the black wire from the switch - I did that and shifting worked perfectly fine.

Then, after about a 45-minute cruise, right as I backed off the throttle (before even hitting neutral), the engine shut off instantly and hasn’t fired since and the problem is no spark.

What I’ve checked and done so far:

• Engine is getting no spark.
• Replaced the pickup coil/module inside the distributor with the new fully-enclosed style (no change).
• Verified coil positive (purple wire) has 12 V with key on.
• Verified ground to the ICM (black wire).
• Tried bypassing the knock module – no change.
• Coil seems to be working (I swapped with my old one and no change).
• Tach started bouncing up and down while the actual RPM were steady (at idle the tach would go up to 3K RPM and back down to 1K)
• Disconnected the main engine harness, jumped 12 V directly from battery to coil +, jumped the starter solenoid studs – still no spark.
• Test light between coil + and coil – dims but does not flicker while cranking although it’s got an incandescent bulb and thus may not pick up the quick pulses an LED test light would.

The ICM (riser-mounted box) has “5.7 Bravo” printed on the back as it came from a boat with a Bravo outdrive but it’s now paired with my Alpha outdrive, so I’m wondering:

• Could using the Alpha shift-interrupt switch with a “Bravo” ICM have damaged it?
• Or does that not actually matter as long as the shift interrupt switch was installed?

Hopefully somebody on here is super familiar with the T-Bolt 5 ignition system or had a similar issue and can chime in as I feel like I’m hitting a dead end here except for ordering a new ICM. Thanks in advance for your help!!

in addition to testing above. A bravo module is not made to work with a shift interrupt, so i dont think it will go out of gear.

I test ran my engine when I repowered with a bravo module (alpha set up as well. If I recall it worked with the bravo module with the shift interrupt wires from the harness plugged together. I got a alpha module after that so I am not sure if it can be made to work with a NC switch? If you still have the alpha module off the old engine try that after you go throught he troubleshooting guide above

 

[Marko_f1]

Could be Tach is shorting out or interruptor switch is staying engaged

Disconnect the Tach and the interruptor switch

If after that there is still no spark run thru this test
View attachment 412758

I disconnected the grey wire from the coil negative terminal (tach wire) as well as disconnected the tach from behind the helm and still no spark. I did run through all those tests and it seems like the ignition module is the culprit.

A mechanic that’s done this before, told me to convert to the electronic (HEI) distributor system instead of just replacing the ICM. Supposedly it makes the engine run much smoother and cheaper to maintain.

 

[Marko_f1]

in addition to testing above. A bravo module is not made to work with a shift interrupt, so i dont think it will go out of gear.

I test ran my engine when I repowered with a bravo module (alpha set up as well. If I recall it worked with the bravo module with the shift interrupt wires from the harness plugged together. I got a alpha module after that so I am not sure if it can be made to work with a NC switch? If you still have the alpha module off the old engine try that after you go throught he troubleshooting guide above

So I actually tapped the white with green stripe wire from the interrupt switch to the same colour wire going from the distributor to the ICM and it was shifting perfectly fine. Whether that had something to do with the no spark issue or not I’m not sure but inward able to shift out of gear easily after wiring the switch.

 

[Scott06]

I disconnected the grey wire from the coil negative terminal (tach wire) as well as disconnected the tach from behind the helm and still no spark. I did run through all those tests and it seems like the ignition module is the culprit.

A mechanic that’s done this before, told me to convert to the electronic (HEI) distributor system instead of just replacing the ICM. Supposedly it makes the engine run much smoother and cheaper to maintain.

A lot of folks will use a Delco EST to replace the complete TB system when the module dies due to TB module cost/ lack of availability. The Delco is an OEM quality system and modules when they die are cheaper, although we have seen folks on here getting bad EST modules or having trouble putting it in base mode/not coming out of base mode.

Not sure who said it would make engine run smoother, the TB system mis excellent except for the fact that the modules have always been pricey and as time goes on many are NLA. If you look on ebay you will usually find a few. I bought a spare years back for $200, just saw a 5.0 alpha module for around $350. I think the 5.7 module has a little more total timing but willing to bet a 5.0 module will work fine. I have used both 5.0 and 5.7 modules on my 5.0 carbed engine no issue

 

[Bt Doctur]

do the test of the white/green striking a ground. If you get spark the module inside the dist went bad. and is economically replaced .
If your switch is a N/C type then to make it work it needs to be spliced in series with the coils purple wire to interrupt power the normally open switch grounds the neg coil post