Re: Thunderbolt IV Problems
First of all, all you guys are awesome for taking time from your busy lives to share your extensive knowledge with guys like me. Thank you so much.
As far as the rotor goes, it's the correct one. But we did find the REAL PROBLEM!
I wish I could take credit for finding the clue that solved the case, but it really was a very mechanically inclined co-worker who noticed that the distributor cap was warped badly. After closer inspection, we concluded that the cap was installed incorrectly. This is what happened:
While rebuilding the engine the first time, my haste and inexperience caused me to overlook the alignment tab for the distributor cap-to-distributor body connection. I clocked the cap incorrectly and tightened it down. Apparently I did not tighten it so much to cause enough warpage to make it malfunction. Therefore it ran well last year. But after tearing the engine down for the cam swap I reinstalled the distributor cap in the same position as I removed it. This warped it enough to cause the ignition malfunction that started this thread.
After buying a new distributor cap, I installed it in the same position as the one I removed. This damaged the new cap, causing the same condition as the previous one. Only after installing another new cap in the CORRECT position did the ignition problem cease. I put the old coil and amplifier back in and it runs great.
Note: DO NOT SIMPLY THROW MONEY AT THIS PROBLEM... IT WILL GET YOU FRUSTRATED AND BROKE! From what I hear, the Thunderbolt IV is a very good ignition system. Test, retest, check, and recheck everything thoroughly and determine with certainty what is causing the problem before purchasing parts. I replaced the entire Thunderbolt IV system (except wiring harness and distributor body) without solving a single thing. Granted, many of the parts were due for updates or replacement, but some were not. If I would've bought a new amplifier unit from mercruiser I would've spent $560 for nothing. Please, don't waste your time and money by replacing parts without knowing for sure that they are faulty.
This leads me to pass along some humble advice to anyone else who may encounter this sort of problem in the future. The process of fixing stuff often is a journey in learning. Always check to make absolutely sure all work performed on your boat is done correctly the first time. If you are doing it yourself, take your time, inspect the original equipment THOROUGHLY as you disassemble it and replace parts EXACTLY as they were removed.
My very best to all of you who are willing to get your hands dirty and you who are willing to help others who want to, too.
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