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Alternator Rebuild 55 Amp to 110 Amp

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  • Alternator Rebuild 55 Amp to 110 Amp

    I have just about finished a 1995 Mastercraft Maristar (LT1 engine) project. I’ve added a ballast system, upgraded the stereo, and a bunch of other things...Probably will detail my adventures shortly. However with all the new electronics, my 2 (new) batteries can’t keep charged on longer trips. I plug into shore power and recharge after each trip, but when I can’t do that, we have to limit the stereo usage (which is unpopular) or we run the batteries down.

    So I found a local shop that can rebuild the alternator and get about 110 Amps output. I cant find a wire harness kit or anything for this engine/alternator to handle the extra output. But I was reading on another thread that some people have simply added an additional, heavier gauge cable along the current cable run, instead of replacing anything. From researching, sounds like 4AWG cable needs to be added.

    Does this sound reasonable?

    Which cables (in the picture) need to be changed, upgraded, or piggy backed on?
    Attached Files

  • #2
    My suggestion; 8 AWG is sufficient if you insist on upgrading. However, in some instances I have kept the OEM 10GA orange wire and have never had any problems. That scenario was going from a 51 amp to 105 amp. output. I am currently using a 10 G wire for charging a dual battery setup from a 105 amp alternator. Works just fine for me.

    Orange wire is the one you want to address.

    Often I will route a new wire outside of the wire bundle and abandon the original in place, then run the new wire to it's destination in a clean and tidy manner. Most times it is not worth trashing out a bundle of wire to try and swap wires. Just run the new wire along that route or similar as long as is reaches its proper destination.

    Just make sure the local re-builder is cognizant of the marine application that you need for the upgrade.

    US $0.02

    .
    Last edited by waterlogged882; 04-10-2021, 10:14 PM.
    93 190
    (safe click)

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    • #3
      Odds are, the alt output terminates at the starter, so its maybe......3ft? Find a current draw chart and see what gauge is required for the apx length and 110A potential. 8ga sounds about right, but 4ga is overkill x 2.

      In the pick the orange is the output cable. Id upgrade rather then piggyback.

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      • #4
        8 AWG it is if I upgrade it. Thanks for the detailed responses!

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        • #5
          From what I've found with the factory wire it isn't necessarily that its too small its that the condition of the wire at both ends at the crimps tends to be poor and if you want good juice and are going to crimp new ends on you might as well build a new wire. My favorite is to pull the wire and take it down to NAPA and have a new wire fabricated professionally with tinned marine wire + high end terminals.

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          • #6
            What is the output at idle? I'm having some trouble with the original alternator after putting new brushes in it and the LT1 needs at least 12.4 coming out of it - according the gurus at Technical Services because I called them today to discuss some hesitation in reverse. Got the alternator hooked up but output at idle is 11.84vdc, 675 rpm. Looked at DB Electrical and going to look at ARCO as well. Switching to a 70-110 amp alternator, but looking for 12.8 - 13v output at idle to 1000 rpm.
            1993 25th Anniversary Limited ProStar 190, #17

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            • #7
              Got the alternator hooked up but output at idle is 11.84vdc, 675 rpm
              Heres the conundrum, the alternator can not actually put out less then what the battery level is. A fully charged battery is 12.8. A charged but aged battery is normally about 12.5'ish/ So if you alternator's "out" is 11.84V, then its not doing squat, thats just battery voltage.

              What happens if you bump the idle up a couple hundred rpm?

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              • #8
                I'll check that this morning...but probably going to take the alternator into the shop to test, get a new battery, and get some 8 gauge wire in case I get a new 70-90 amp alternator.
                1993 25th Anniversary Limited ProStar 190, #17

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                • #9
                  Can anyone tell me where the excited wiRe goes back to or where it gets it’s ON source? Voltage is low - 10.94 when tested this morning
                  Last edited by bret; 04-15-2021, 09:54 AM.
                  1993 25th Anniversary Limited ProStar 190, #17

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                  • #10
                    Originally posted by bret View Post
                    Can anyone tell me where the excited wife goes back to or where it gets it’s ON source? Voltage is low - 10.94 when tested this morning
                    I cannot be certain about the excited wife.

                    The orange wire typically goes to the engine breaker, then to the starter relay or the solenoid on the starter. At that point the battery lug and the orange lug should meet, thus re-charging the battery. Your mileage may vary but not by much.
                    On newer single wire setups, I think the exciter is built in and is triggered by a certain minimum RPM. Don't hold me to it but that is how it works on the Ford engines.

                    .
                    Last edited by waterlogged882; 04-15-2021, 09:48 AM.
                    93 190
                    (safe click)

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                    • #11
                      Sorry about the WIFE WIRE . was on my cell getting alternator tested - GOOD. Battery being tested but I have other house stuff today with remodel. Will pull circuit breaker off, run a new orange wire, then trace Purple Exciter wire back and may run a new one of those to see if I can find the voltage drop.
                      1993 25th Anniversary Limited ProStar 190, #17

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                      • #12
                        [IMG][/IMG]

                        New 8 gauge wire, then 10 gauge on exciter WIRE, just have to find the purple wire termination in the harness. I have purple and orange electrical tape and I'll cover those at each end of the harness when I install tomorrow.
                        1993 25th Anniversary Limited ProStar 190, #17

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                        • #13
                          double check that all the screens and shields are still on it...

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                          • #14
                            To follow up on my problem, alternator shop - the owner did not test it(some kid did) and he gave me money back because a spare from a friend worked great! 14.2 output at idle, 13.4 at the battery.
                            1993 25th Anniversary Limited ProStar 190, #17

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                            • #15
                              Originally posted by bret View Post
                              To follow up on my problem, alternator shop - the owner did not test it(some kid did) and he gave me money back because a spare from a friend worked great! 14.2 output at idle, 13.4 at the battery.
                              Good for you. You're back in business.

                              .
                              93 190
                              (safe click)

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