I am installing a 2005 496 Mag HO where there was a stock 2000 7.4 MPI. I noticed that the 9 pin connector is exactly the same and that should be no issue but on my boats harness I have 2 red wires that are not part of the 9 pin. On my 7.4 one of them went to the Mercathode and the other to a breaker switch that was bolted to my riser. New engine does have a breaker but it is wired internally on the motor and same for the mercathode. Where and/or what do I do with these wires? Do I need to splice them in somewhere? The guy who I bought the motor from does not have these two extra wires on his harness. Electrical is my weak point so any help on this much appreciated.

Thanks

I'd tape them up for now.unless something on the boat side needs 12v.then hook them up .

If the Mercathode is already wired, then just cap off that wire. Did the other engine have a switchable exhaust? Maybe that is what the other hot lead is for. As Sutphen said, cap it off for now. Everything you need should be in the 9 pin.
Eddie

Actually, I made a mistake... (I just posted again because I did not see this one listed)... One of the two wires running along with that main harness is the positive for trim pump... the other went to the breaker. I have another wire that runs off my battery switch up to the mercathode. Wondering if that will need to be connected somewhere in order to get power to the motor. That wire once broke and with the old motor it cut off all power to starter.

Thanks for the help though guys... appreciate it!

trim pump wire should run straight to your batteries or battery switch.mercathode wire could get its power from the circuit breaker.should clean up your wiring by the main plug

Thanks guys... engine goes in next week we'll see how I do.

As stated, do you have diverters? That would explain the breaker on the riser.