4.3 L electrical question

[Skyking 310]

I'm stumped! I have a 1988 Sea Ray 27' Sundancer with twin 4.3L Mercrusiers. I (actually a marine repair shop) recently swapped out the old 4.3's for two 1997 Vortec EFI motors. Everything about the engine swap went fine EXCEPT now the voltmeter (ammeter) gauges in the instrument panel don't work. Zip. Zero. Nothing.

The mechanic who did the engine swap has tested the gauges (they test OK). He believes there is a "short" and rather than try and troubleshoot the problem, he wants to run new wires from the batteries to the gauges. His motto is "When in doubt, re-route!" I'm not so anxious to do that. They worked before the swap without any problems, so I'm thinking he either hasn't connected something or has something connected incorrectly. The problem is, electrical issues and me are like oil and water. In short, I don't have a clue where to begin. Does anyone have any suggestions?

Thanks in advance!

 

[Don S]

Re: 4.3 L electrical question

Running new wires is a hack repair, the volt meters (ammeters haven't been used since the early 70's) pick up power from the ignition switches "I" terminal (purple wire) along with all the other instruments. Ground is also tied to all the other instruments.
Here is a typical wiring diagram of the instruments.

View attachment inst wiring.pdf

 

[Skyking 310]

Re: 4.3 L electrical question

Thanks, Don, especially for the comment about it being a "hack" repair. That's exactly how I feel about it. I'll use the diagram and do some checking on my own.

 

[Skyking 310]

Re: 4.3 L electrical question

Don, do you know if the wiring harness on the new motors (1997) vs the wiring harness on my boat (1988) are different? They both have the same number of "pins" and plug in without any difficulty, but I'm wondering if everything is the same, especially because the new motors were EFI and the old motors were not.

Thanks

 

[Don S]

Re: 4.3 L electrical question

Should all be basically the same. The purple wire goes from the switch to one of the instruments, then from gauge to gauge until they are all connected. From one of the gauges the purple wire goes to the ignition.
After 20+ years, who knows what previous owners have done.

I can only say how it should be done, because I can't actually look at yours.