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Any reason why I SHOULDN(39)T have done this...-gctid827856

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  • Any reason why I SHOULDN(39)T have done this...-gctid827856

    Rather vague post title, sorry... but a proper one took up too much space.

    A recent replacement of my house bank single 12v with dual 6V GC batteries prompted a more extensive revamp of my whole electrical setup. After reading extensively on here and elsewhere, decided to get a new Blue Seas 25A charger and add in their Add-a-battery kit... so my bog standard MBSS was replaced with their Dual Circuit Plus switch and their SI-ACR. Here's a pic of the end result, installed in the transom locker:

    Everything works great.... the charger even has a feed into the ACR which de-activates it (isolating the 2 banks) while the charger is running... this allows the charger to independently control the charging stage of each bank.

    However, I realised that one of the bigger selling points of this setup... start isolation... wasn't working. All my electronics were still power cycling when I started the engine. I'm sure this isn't news to the experts out there, but I realised that all my 12V electrical stuff at both helms is being fed from a + & - wire within the main electrical harness that connects at the engine. Under my original MBSS setup, this meant that everything would powered according to the switch position. Under my new setup with the ACR, it meant that under most circumstances, all my gear would ONLY be powered off my start battery. To correct this I had originally decided to run new 8 gauge wire pairs to each of my accessory panels at both helms, taking them off the switched 12V fuse panel coming off my new selector switch (left side panel in the pic above). However, as I started tracing wires and preparing for the P.I.T.A. task of pulling 2 lengths of fairly thick wire to my helms I suddenly thought why not use the existing feeds in that main harness? So... with some trepidation I isolated and cut wires 1 & 6 (Red with purple stripe and black) within the bundle that comes out of the male plug, having referenced these in my mercruiser manual, see below for diagram. I then ran the Black directly to the ground stud on the engine block and the red to the switched panel, and used a 40A fuse. I taped up the bare ends on the cut wires in the harness plug and plugged it back in.

    In short, this seems to have accomplished everything I was hoping for. All electronics and accessories that were originally fed off the engine harness are now fed directly from my switched accessory panel. Start isolation works... my electronics don't recycle when I start the engine. Everything that I could think of to test seems to works perfectly. I am wondering if there is anything else I might have affected by doing this in this manner... any reason I should revert my change and go back to Plan A, running independent wires to the helm fuse panels?

    Tyson, Ackerley, Sidney & Gene
    Tsawwassen, BC
    1996 2858 Ciera Command Bridge - "Island Passport"
    Mercruiser 7.4L (GEN. V) GM 454 V-8; Engine Serial 0F603347
    BRAVO III retrofit
    Home Marina: Tillicum Bay Marina, Sechelt Inlet, BC

  • #2
    Can't really say as I can't see the wiring diagram. It's too small. But if EVERYTHING works I'd say your fine. If the black box is your battery charger it's gong to need more ventilation than it's going to get inside a compartment.
    1986 Bayliner Contessa 2850
    In over my head for sure!!
    M/V SKUA refit