Help with OMC 3.0 alternator wiring

I just replaced my transom, and after reinstalling the motor, I can't figure out what the previous owner did to wire the alternator. It is the original marine alt, and appears to have four connections...I only have 3 wires. Can someone tell me how this should be? <br /><br />On the rear, looking at the alt from the back of the boat, are four stud terminals. On the upper left side there is an isolated terminal (black boot) labeled "AC TAP"...just below it (1/2") there is an un-isloated connection labeled "IND LIGHT TERM"...at the bottom, off the regulator, is an unlabeled terminal. On the upper right side is an isolated terminal (red boot) labeled "POS OUTPUT." When I say isolated, it has that plastic through case grommet/spacer/whatever to keep it from shorting on the case.<br /><br />For wiring (original harness as far as I can tell) there is a large orange wire with a ring terminal...I know this goes to the "POS OUTPUT". I also have a small purple wire with a ring terminal (don't know where it goes) and a small red wire with a spade terminal...there are no spade terminals on the alternator that I can see. (The only thing I can figure is there was a ring connector on one of the studs that had a connector to accept the spade.)<br /><br />The previous owner had the purple on the "AC TAP" and the red wire disconnected but I can't believe this is correct. Any help?

Re: Help with OMC 3.0 alternator wiring

Jay....what year is this, is it a Motorola alt and is the engine a Ford? My books say the 4 term should be labelled POS, EXC, S and AC. Fords use the AC term with a purple/white wire going to the choke, POS is the orange wire like you said, the S has a purple wire that goes to the ESA and the EXC has a purple/red wire that goes up the ignition switch for the ON position.

Re: Help with OMC 3.0 alternator wiring

It's an 1986 OMC 3.0 (GM 181 cid.) I think the purple wire does have a white stripe...I really didn't look hard enough. As far as I know, there is no wire going directly to the carb for choke...all the alternator wires came off with the harness while I replaced the transom (wiring harness stayed in the boat) and there was nothing attached to the carb. Of course that assumes it's original...no telling I guess. BTW, It is a Motorola alternator. Thanks for the help!

Re: Help with OMC 3.0 alternator wiring

OK Jay...the book said that only Fords used the purple/white wire for the choke. I'll check the book again tonight but I think the only difference was the AC term is not used on a GM engine otherwise the rest of the wiring is the same.

Re: Help with OMC 3.0 alternator wiring

Jay...I checked again and the 3.0 ltr only uses the 3 posts on the alt (no AC). I can scan the engine wire diag for you if you want, let me know your email so I can send it to you.

Re: Help with OMC 3.0 alternator wiring

Thanks Bob! Email is jmwj03 at hotmail dot com. I got everything else running and rewired today...even built a new engine cover and carpeted it. The only wires that aren't connected are the alternator! I really appreciate your help!

Re: Help with OMC 3.0 alternator wiring

OK...Jay, hopefully "You Have Mail" if not let me know.

Re: Help with OMC 3.0 alternator wiring

LOL...I looked over it 3 times because I was looking for the sender to be "Boatin Bob" Looks great, but I can't quite read the labeling. When I blew it up, it got too fuzzy..<br /><br />On the alternator...starting in the upper left corner & going clockwise, I can't read the 1st and 4 the connections. The other two I can figure out...I'm pretty sure #2 is the AC and #3 is the POS. Mine isn't quite laid out the same way...3 of my connections are on one side and the POS is all by itself, so the labeling will be important. <br /><br />I also can't make out the color code...since it is mostly dotted and dashed lines they all kind of ran togother. I'm going to clean out my inbox to make room, and why don't we try it at full size to save you from having to try and decipher it all for me. I'll send this via email as well.<br /><br />Thanks again Bob!

Re: Help with OMC 3.0 alternator wiring

Jay...sent you another version which wasn't shrunk down as much and should be clearer when you zoom in. For the connections the top left is the EXC, top right AC, bot right POS and bot left S.