Alternator wiring

[Lakerider]

I have a 1997 Larson with a4.3L gl engine. I am wondering if my tach is wired to my alternator
My wires are purples and white to terminal P. Then green to terminal L2. Another purple to exc pigtailed to S. And an orange to main + and a black to neg. I am wanting to change to a higher amp alternator and need to know if I need a tach wire or not

 

[dannys2004glastron175mx]

Your Tach wire should be gray and hooked to your coil

 

[wrench 3]

No tack to worry about, but the purple with white operates the choke and the green holds the fuel pump on.

 

[Lakerider]

Thanks I will check tomorrow and see if there is a grey and white wire running to the coil and the tach
I don't know what all the wires are on the original alternator to know how to wire up the new three wire high output alternator

 

[Lakerider]

Wrench 3.
So if I get a new alternator and it has 2 wires Besides the main charge wire. One that is 12+ sensing and another that is 12+ when engine is running. What do I do with the purple wire that is pigtailed coming frame somewhere else straight to the EXC terminal and pigtailed to the S terminal

 

[wrench 3]

The purple wire is the one that is 12+ when the key is on. The 12+ sensing terminal can be jumped (pigtailed) to the battery terminal (main charge).
The choke and the fuel pump relay could probably be hooked to an oil pressure switch. I could tell you how to wire that but I haven't had any experience as to how well it will work on your engine. May be some one else will chime in who has tried it.

 

[Lakerider]

Thanks a ton
Maybe someone will chime in as you said
I feel like the 3 wire alternator will work with some creative wiring. I don't know where the oil pressure switch happens to be or even looks like. But I am sure someone does That's the great thing about this forum

 

[wrench 3]

I don't know where the oil pressure switch happens to be or even looks like. But I am sure someone does That's the great thing about this forum

Your engine doesn't have the oil pressure switch from the factory. Just a sender for the gauge and maybe a single wire switch if you have an engine alarm. On your engine they are usually down to the back on the port side, just above the oil filter. You would have to tee in the extra switch.
As I said, I can tell you how to hook it up. I just don't know how well that system would operate your choke and fuel pump relay.

 

[Lakerider]

I believe it does have oil pressure sending unit. It has an oil pressure gauge and its electric. Is that not the same thing?

 

[wrench 3]

I believe it does have oil pressure sending unit. It has an oil pressure gauge and its electric. Is that not the same thing?

No, the sending unit only provides a variable ground for the gauge. The switch that you would need turns things on and off like a light switch. It switches on when there is oil pressure and off when the oil pressure drops. Your old alternator was being used to turn those things on when it was charging and off when it wasn't. The only problem is that I don't know if it was using 12V DC to do that.

 

[Lou C]

Can you find an engine wiring schematic for your engine? That will probably answer your questions.
I just replaced the alt in my old '88 OMC and got an exact replacement from Arco Marine.