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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11075
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I own a 1993 omc ford cobra 5.0 EFI I bought a alternator model

Customer Question

I own a 1993 omc ford cobra 5.0 EFI I bought a alternator model 18-6260 sierra I notice that they where about 7 to 8 post I toke back to west marine and they told me it was the wrong model so they order a new alternator model 18-6261 it looks the same as the first one I have three wires to my alternator, purple (exc) and a orange (pos) black (Grand) my problem is that the new alt has a EXC post and a P post im assuming that the P stands for positive but there is no G for ground
Submitted: 2 years ago.
Category: Boat
Expert:  Tan replied 2 years ago.
Hello. My name is***** alternator will ground through the case. Many alternators have the ground connected to one of the case screws. There is no actual labeled ground. Does this make sense?
Customer: replied 2 years ago.

the only two screw that are on the case have a letter (E) and (2L) this is also my problem the ground wire this is a photo of the first alt the same as the second alt

Expert:  Tan replied 2 years ago.
The only wires you need connected are the exc, pos and ground. The other letters are not to be connected to anything. The ground connects under one of the case screws not terminal screws. The case screw used for ground is circled in red. The E and the 2L are not related to anything for you to connect. These have to do with the alternator itself. Do you follow these instructions.
Customer: replied 2 years ago.

so the (p) stands for positive and the red circle is for grand thank you very much when I get the alt on Friday ill let u know how it goes lol

Expert:  Tan replied 2 years ago.
Correct. The OMC diagram doesn't even show a ground. From all the alternators I have done over 40 years they have Positive(orange wire) which connects to the battery terminal of the starter. Then the EXCiter wire purple wire. Then the ground to case or through engine block where it bolts to the engine. Technically you could leave the ground disconnected and it will still charge.