I'll throw my experience in here, maybe it'll help, maybe not. I tried running the original Thunderbolt (external coil with electronic pickup distributor) on my stroker. Lots of people swear by them. I had ALL of the exact same symptoms, and every other part of the motor and fuel system were new. I worked through fuel tank and fuel pickup, bypassed fuel pump with electric, had the new carb apart at least five times adjusting float levels, checking fuel levels, so on and so on. Took the distributor apart twice, switched it with another and had it apart twice as well, and switched coils back and forth with each distributor. Always the same issue you are having, regardless of what I changed. I went to Pep Boys, spent $130 on the MSD Street Fire HEI style electronic distributor. One wire. Fixed. Not just fixed, but WAY more power, throttle response, and much better idle and starting, compared to the other setup on it's best day. I know you have alot invested, but there is an example of things I tried with no results. Maybe you can get your money back? Or maybe you can ebay it. Try the HEI that was offered, even stock they are pretty good units. Might be a fast solution to get back to boating. Like I said, some people swear by the external coil setups of all different kinds, and that's great if that's what they like, but I'll never do anything other than an HEI style again. Too simple and too reliable for me to bother risking it.
