Bruce
Should I get one of the alternaters off of the other motors? Might be worth a try, at least it would eliminate them as being the problem.
Mark

Hey Mark

No, I won't need it this weekend.

Thanks

sounds like a short?.....sounds like possibly your battery is bad and grounding itself out.....

I don't think a battery would know the difference between 4500 and 4700 rpm and act diferently. The higher rpm's input to the altenator migh be finding the limit of a week diode in the altenator. I'd try another altenator or disconnect it for a run and see if running on the battery will take you over 4700.

I know.....anything can happen.

Just think its odd that I take the old motors out (the port alternater quit working this year), install these 70 hr. 502's, and I still have problems with the port side. The voltmeters are reading over 14 volts, except when I use the drive trim. The port drops more than the starboard, but comes right back.

I still say the drive trim should be hooked directly to the battery, instead of the positive hooked to that starter lug. The drive trim is on a 110 amp fuse. With it hooked to the starter(with 90 amp fuse), would it be likely the 90 amp would blow?

Weird

Will have to do some testing with the meters and on the water(spare fuses are ready!)

Thinking back on that first run with the new power, we were looking for top end. I could have been on the trim at that rpm range.........but I can't remember

Bruce

If you can tell me what year and model the boat is, what you had to modify to install the EFI 502's (if anything) if you are using the ECM's from the installed 502's, had to modify the main engine harness for the EFI motors etc, I can probably help. If a 110 amp trim motor is being ran through a 90 amp breaker or a fuse, it's likely to blow, and if you give me some specifics (i.e. runs funny at 4700 using no other acessories and only blows the fuse when operating the trim or?) I have ALL the Mercruiser factory wiring diagrams and diagnostic procedures for anything you may have, and can walk you through the steps nesessary to find and resolve your problem, but direct questions and answers are needed because I can't see what you have. If you don't need the help, thats ok too. I also have a legend of all Mercruiser wire colors, and their functions for most boats as well.. I may put up a web page with some of this info so you guys will have some much needed resources that are reliable and accurate to help out, but that will take a little time... Just for the record, I eat, sleep, and feed on solving complex electrical problems, and do it very successfully for a living... (for whatever that's worth)...Let me know, if you can "FindMe"...lol

Thanks FindMe

Zero electrical mods were done. The engines were complete. The only modification was to the fuel cooler bracket to get it to fit with the offshore mounts.

I'll be diagnosing and running the boat this weekend. If we fail at figuring it out, I'll take you up on your offer to help and be as specific as I can about the symtoms.

Oh yeah

1994 Pantera 28 with 2001 502's

Thanks
Bruce