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This is what I was talking about...
By Mike (bigdeal) on Wednesday, April 21, 2004 - 2:39 pm:
Hey all... This thread got me so interested in this issue that I decided to take some time at lunch today and call Indmar's tech support to see what they'd tell me. Here's what I learned from my phone call.
Indmar has a 70 and a 90amp alternator upgrade kit available for purchase through your local dealer. The kits are pricey at around $300+. With either kit, you get the alternator, a new set of mounting bolts, and here's the kicker, a new 'harness'. The new harness is essentially a single larger diameter wire (he thought 8awg) with ring terminals on both ends. Indmar's instructions that come with the kit instruct the installer to:
1-Remove the existing power wire (orange) connected to the output leg of the alternator, the exiter wire (purple) and ground wire (black).
2-Remove the existing alternator and replace it with the new one using the supplied hardware.
3-Reconnect the ground (black) and the exciter (purple) wires to the new alternator. Wrap back the original power wire (ornage) as it will not be used.
4-Take the 'new' wiring harness provided with the kit (remember, a single larger gauge wire) and connect it to the output leg of the alternator. Then run it around the rear of the motor and 'past' (i.e. not through) the existing main breaker on the back of the motor, and connect the free end to the back of the starter.
Of course the instructions assume the 'new' alternator is a three wire setup. My new alternator is internally grounded, so I didn't have to use the black ground wire that was connected to the original alternator. If your new alternator is self-exciting, you won't use that wire (purple) either.
According to the tech rep, no breaker between the alternator and starter is necessary. And as to the issue of running a larger amount of amperage across the back of the starter, he said that the starter draws approximately 125amps from the battery at startup, so my 100amp alternator was not going to do it any harm. Given this wiring setup, there will be no breaker on the main power loop (i.e. from the alternator, to the starter, to the positive terminal on the battery), which Indmar feels is ok. He also mentioned that the stock 50amp breaker in my boat was actually wired downline of the main power loop we were discussing, and as such should absolutely be left in place as is. This 50amp breaker only protects the main wiring harness from an overload, nothing else.
I further asked whether there'd be any advantages to installing the new 135amp breaker I have between the alternator and starter to protect the starter and/or battery from damage if the alternator went bad. The Indmar rep really didn't feel there was any advantage to installing it, but it would not hurt anything if I did. He said the likelihood of the regulator in an alternator failing in such a way as to allow an unregulated flow of current to the starter/battery is highly unlikely. It would also be immediately evident throught the charge meter on the dash. According to him there have been virtually no cases of this happening.
The result of my conversation today was that I have some issues to address in my wiring setup before I go boating again. Namely, I need to put back the original 50amp breaker at the rear of the motor, and to make up a 'new' 4awg wring harness to run from my alternator to the starter. And yes, because I have it (and I'm hopelessly anal) I'm going to install my new 135amp breaker in my 'new' harness between the alternator and starter. It can't hurt to have all the prtoection you can.
Anyway, I hope this helps further explain what needs to be done to install a new high output alternator. I know I learned a lot today.
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