alternator wiring - red and black wire Mercruiser 78403A2

[crestlinercrusader775]

Hi,

I have ordered a new alternator for my boat (Mercuiser 140 HP engine, an older one). Now I am wondering what to do with the red and black wire (see picture). I think the red is the sensing or trigger wire, and black goes to switched 12V+ (ignition).

part number of the alternator is 78403A2

Am I correct?

 

[Bt Doctur]

excite to the left, sense on the right

 

[crestlinercrusader775]

Ok, so like in this picture:

 

[Eric 3.7LX Alpha 1]

#1 is your ignition feed
#2 is a sense wire that controls the internal voltage regulator to goes to battery or could be run up to the helm to read battery voltage there, but you don't have to. You could have say 14 volts coming out of the alternator and 13.5 volts at the helm due to voltage drop in wiring.

What are Remote Sense Alternators | Delco Remy

Remote Sense utilizes a second wire that reads the actual voltage at the battery and signals the alternator to increase its voltage output to compensate for the voltage drop, ensuring a constant 14 volts at the battery.

www.delcoremy.com

#3 is the charge output.