Electrical demons!
 

1994 Powerquest 257. Going through coils like crazy. New engine (465 HP 454) as of this Sunday (Boat sat inside, covered for 2 years). First ran it on Thursday, ran about 1 hour and the Blaster high Vibration coil went bad (no spark to distributor). Replaced with an old stock coil I had laying around and that one lasted about 45 minutes. Put in another old stock one and it'll start, but won't stay running. Check, check and recheck all connections? MSD 6AL box bad? Gonna replace it with the one from my Camaro. I know that one is good. Am I barking up the wrong tree? Really getting frustrated. Two trips on the water, two tows!

Bypass you msd for starters. if still having problem, check distributer for excessive corrosion. good luck.

I have a similar problem in that I blew 3 ECM electronic controll modules in my distributor last summer. Mechanics said it was because I was running on 2 batteries. That is what Merc told them that I sould only run on one battery at a time for a 454 Mag EFI 1995. I had run on 2 batteries for 8 years no problem. Since I started running on 1 battery this year no problems yet. I am kind of frustrated that I don't think we ever figured out the route cause but I don't want to keep blowing $100 parts. If any one has any ideas share. thanks!

Read on another forum that my problems probably started when I tried fast charging an old battery. Too many volts and not enough battery to contain it, so it went through the rest of my electronics. Changed the box and put in another coil. Another burnt up coil! Now I've changed MSD 6AL, coil (several times), starter and that left the distributor. Took out my HEI pertonix unit from my Camaro and put it in, and everything seems to be fine now. Runs good and restarts just fine. Problem solved....sort of. If the distributor's magnetic pickup got hit with extra voltage from the battery charger will replacing it make the MSD distributor good again. Is there anything else I need to replace in the distributor? Should I just get a whole new unit? I don't want to leave the pertronix in because it's not marine grade. Also, any preferences on mechanical or vacuum advance?Thanks, guys for any ideas.

I've always heard mech. adv. I'd throw all of the MSD stuff in the trash!! Never had any long term good luck from MSD. Go back to merc. thunderbolt !!