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Engine wiring 1979 228 Mercruiser ??

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  • Engine wiring 1979 228 Mercruiser ??

    Hi Guys - hoping someone can help me - I'd like to upgrade to a higher amperage alternator - but want to check out the engine wiring for my merc beforehand - and am looking for the schematics - I've looked in the stickies with no success - maybe I'm missing something - and my seloc manual gives little help.

    Anyone give me advice on where to find the wiring schematics ??

    Please & thanks in advance - Matt.

  • #2
    the standard alt works just fine and as far as the wiring what amp output are you working with. #6 wire is more than adequate from the output post to the starters post.
    NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

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    • #3
      Originally posted by Bt Doctur View Post
      the standard alt works just fine and as far as the wiring what amp output are you working with. #6 wire is more than adequate from the output post to the starters post.


      Yes - I know the alternator works fine - stupid I'm not - however - I'd like to be able for my alternator to run some new electronics I've installed - so the 50 amp or so output will be insufficient or running at it's limit - and I'm not comfortable with that. I'm not going into specifics- I've asked a simple question - just hoping for some help.

      So if you can help me out with a detailed ele schematic - much appreciated.

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      • #4
        even a full boat of todays electronics the power needed will be covered by a standard alt. If worried about a weak starting batter, install 1 or 2 dedicated house batteries for the electronics.
        click to enlarge

        NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

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        • #5
          you have an amp meter. you are limited by that, so no reason to go bigger with the alternator.

          or re-wire your boat/motor to go bigger alternator.
          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

          Past Boats
          1970 Wooster Hellion - Merc 9.8
          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

          What’s behind you doesn’t matter.Enzo Ferrari

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          • #6
            Originally posted by Bt Doctur View Post
            even a full boat of todays electronics the power needed will be covered by a standard alt. If worried about a weak starting batter, install 1 or 2 dedicated house batteries for the electronics.
            click to enlarge

            Actually the above might help me - I'll check to see if the wires match mine ! Thanks
            Last edited by moonrakercat; January 14th, 2020, 01:52 PM. Reason: corrn

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            • #7
              Boat is going to have a 1000 w inverter installed to run 120 electronics also.
              Last edited by moonrakercat; January 14th, 2020, 01:54 PM. Reason: Corrn

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              • #8
                Originally posted by Scott Danforth View Post
                you have an amp meter. you are limited by that, so no reason to go bigger with the alternator.

                or re-wire your boat/motor to go bigger alternator.
                My boat does not have an ammeter - that does not limit current fyi.
                Last edited by moonrakercat; January 14th, 2020, 01:55 PM.

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                • #9
                  A ran a 1200 watt one and at max output 1200 watts of whatever was plugged in , the input current was 100 amps.
                  So you would be looking at 2 large capacity house banks and atleast #1 or #2 wire from the batteries to the inverter
                  NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

                  Comment


                  • #10
                    Originally posted by Bt Doctur View Post
                    A ran a 1200 watt one and at max output 1200 watts of whatever was plugged in , the input current was 100 amps.
                    So you would be looking at 2 large capacity house banks and atleast #1 or #2 wire from the batteries to the inverter
                    I expect to draw maybe 500W from my inverter for short times - but when I do I would still like my 3 house batteries to charge as well as have enough to run the motor - and any lighting if I'm running in the evening - not to mention a few other items. So ideally a 80-90a unit would keep me fine. I could probably run with my existing alternator - but don't want to chance it if I really don't have to. I know I'm going to have to run a few extra wires for the extra current - but I want to double check the schematic for the charging system before I jump in too deep.

                    The schematic you have sent above is much appreciated - it is similar to my merc - but not quite it - the schematic you sent says pre BIA on it - not sure what that means ?? My merc has a Motorola alternator system - I found a Clymer manual that is very close - do you mind if I ask where you found that schematic above ??

                    I really appreciate your help on this - usually I can find things on the web but I'm coming up empty.

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                    • #11
                      Mercruiser Manual 3
                      NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

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                      • #12
                        If you have a voltmeter, then this should be what you're looking for. (BIA is Boating Industry Assoc. In the late 70's Merc adopted BIA wiring colour codes)...

                        With an 80A or 90A upgrade (standard alternator is either 37 or 55Amp, depending on which alternator), I would also increase the size of all the wires running from the alternator output to the battery! By all means, a higher output alternator will be an advantage if you plan on using your high current consumers while under way. But if you are hoping to use the higher output alternator to recharge the batteries very quickly, that's a very bad idea. It doesn't help with how much you drain the batteries, but what it does do is overheat them when the engine gets going. And overheated batteries have a propensity to 'self-disassemble', rapidly (as in, explode)... At the very least it will significantly shorten their lives. If you're going to be draining batteries, leave the standard alternator on.... Cheaper, safer.

                        Chris.........

                        Click image for larger version  Name:	228wiring.PNG Views:	1 Size:	410.7 KB ID:	10825633
                        Last edited by achris; January 15th, 2020, 02:53 AM.
                        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                        The world takes on a whole new perspective when viewed from 100’ below.
                        1972 Bertram ‘Bahia Mar’ 20
                        2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
                        (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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                        • #13
                          achris, that is thermal reconfiguration AND kinetic disassembly.

                          an ACR or a DC-DC charger can charge the house batteries once underway
                          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                          Past Boats
                          1970 Wooster Hellion - Merc 9.8
                          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                          What’s behind you doesn’t matter.Enzo Ferrari

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                          • #14
                            Originally posted by Bt Doctur View Post
                            Mercruiser Manual 3
                            Thanks !!! I take it the manual is in the stickies somewhere ?? I'll have to check it out !

                            Comment


                            • #15
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                              Originally posted by achris View Post
                              If you have a voltmeter, then this should be what you're looking for. (BIA is Boating Industry Assoc. In the late 70's Merc adopted BIA wiring colour codes)...

                              With an 80A or 90A upgrade (standard alternator is either 37 or 55Amp, depending on which alternator), I would also increase the size of all the wires running from the alternator output to the battery! By all means, a higher output alternator will be an advantage if you plan on using your high current consumers while under way. But if you are hoping to use the higher output alternator to recharge the batteries very quickly, that's a very bad idea. It doesn't help with how much you drain the batteries, but what it does do is overheat them when the engine gets going. And overheated batteries have a propensity to 'self-disassemble', rapidly (as in, explode)... At the very least it will significantly shorten their lives. If you're going to be draining batteries, leave the standard alternator on.... Cheaper, safer.

                              Chris.........

                              [ATTACH=JSON]{"alt":"Click image for larger version Name:\t228wiring.PNG Views:\t1 Size:\t410.7 KB ID:\t10825633","data-align":"none","data-attachmentid":"10825633","data-size":"full"**[/ATTACH]
                              Hi Chris - thank you sir ! - that is my exact configuration - I do have the voltmeter - no ammeter and a 50A circut breaker as shown. I wasn't planning on charging the batteries any faster - I just don't want them to discharge with the engine running under my planned loads.

                              However you've brought up a new point - I don't see any mechanism in the schematic above that controls the battery charge rate (I will have 3 batteries charging) - so I assume it is just the alternator output and voltage differential between the alternator and batteries that will determine their charge rate ?

                              I was also concerned that if I had a lower output alternator and was drawing 90-100A from the batteries that the alternator would try to compensate - and possible self destruct itself. I do have an electrical background but will consider it prudent to consult an alternator/starter business for their expertise. I do definitely plan to run another conductor or two to the batteries to compensate for a new alternator output.

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