'89 Montego 3257 with 7.4 Bravo Engine: Replacing the Ignition Control Module

[tkmclm]

Our '89 Montego 3257 has twin 7.4 Liter Mercruiser Bravo 454 engines. The port engine was running rough and it appears it needs a new Ignition Control Module Problem: No parts available. The ICN conversion kit we would like to use is 806961A01, but is our of production.

Any ideas on where to get a replacement ICM? IF not, any ideas on how to replace the ICM with a new kit?

Thanks!

Thomas

[Viper]

Welcome aboard. Can you post your engine serial number.

What exactly is the engine doing? Does it do it all the time or just under a particular condition? What tests/diagnosis have you performed? The more info you could provide the better.

[tkmclm]

Thank you, Viper!

I will need to get the SN, as I don’t have it handy.

The engine starts fine, Port runs rough like it’s missing, and then even after warm up, cuts out and stalls when I bring the RPM’s down to 500 or idle. During a brief shake down run, I could not synch the rpm’s, and the Port engine would not exceed 2500 RPM under load, whereas Starboard ran fine all the way from 0-3000. Each engine has its own fuel supply so I added some fuel treatment, which had no affect. Changed the plugs and wires, checked the cap and rotors, and carb, all in working condition. Still experiencing rough run and cut out.

[km1125]

Do you have fuel selector switches where maybe you could swap the tanks each engine is running from? That'd be a way to rule out a bad fuel issue.

Have you actually swapped the ICM unit from one engine to the other to verify the problem moves with the ICM?

[Viper]

Ya I would try the swap first to confirm or eliminate the ICM. This could be several things.

[plittle2005]

If you have not already done so, remove the gasoline/water separators, pour into jars, see how much water is in each. If a lot, replace filters (sierra 18-7486 likely) and try again. May take several replacements. You may have gotten a batch of watery gas.

The ignition control module in the Delco EST system fails hard, also the pickup coil. Likely not the reason for just rough running.