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  • dual alternator and battery relocation

    • Year: 2008 Brand: Malibu Model / Trim: 247 lsv Cost: $500-$999 DIY or Professional Install: I installed it

    i wanted to run dual batteries in my boat but did not like the available options, not really a fan of the the auto charging relays cause they cause the good battery to charge the drained battery, I don't like the thought of having to flip a switch all the time to switch between batteries, so I separated the power in my boat the ignition and gauges are on one battery then i powered  MUX module and my stereo on the  the other battery and bought a second alternator have the second alternator hooked stereo battery, to add the second battery i was going to just buy a truck alternator bracket the mounts the alternator high and cut off the part of the bracket that holds the power steering pump, but then on ebay a came across a vovlo penta bracket for an 8.1 that mounted an alternator high and it fit perfect, the only thing i had to change was rotate the air filter a little to make it fit and change one idler form ribbed to smooth for the new belt routing, used a tape to get an approximate length on the belt and had Napa order me a few belts and found one that fit,  the next project was where to mount two group 31 alternators so i made some shelf's out of aluminum and hung then in the back on my boat they bolt on where angle on the engine dividers bolt in then driller one hole in the boat to add a bolt towards the side of the boat and made a bracket that bolts the back of the shelf and bolts with hooks (u bolts lift points whatever you want to call them on the back of the boat) then I got 1/4 abs plastic like the engine dividers are made form and bent covers to go over the batteries and to me it blends in and looks factory.








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    Thanks for posting this.  Hadn't seen the batteries in the back like that.   Pretty sweet.   

    Do you have the part number for that volvo penta bracket?   (no worries if not)   Might look into that next summer/winter.    

    Also, the air filter is the same right?   Just on the end of a silicone elbow to make room for 2nd alternator?

    Selfishly it's GREAT to have another 8.1 247 on here.

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    yea stock filter you can just rotate the filter and it clears the alternator but then the tray over the engine does not fit the silicon elbow i just got off amazon and then had to get a piece of pipe to connect the filter to the elbow and i just got some 1/4 alumnium tube and turned it down to fit


    Volvo Penta 8.1 496 Alternator Mounting Bracket # 3819032



    i can get the part number of the belt for you and the pulley was just from advanced the idler pulley from pickup truck with an 8.1


    I remember having to grind something on the bracket but don't remember what it was, but was not much that need ground down i got the bracket form ebay for about $60




    that was the alternator I got 130 amp and I had to add a relay that just connected the excite wire to the charge post and the relay turned on with the ignition i was going to skip the relay and add a oil pressure switch so that the excite wire got power when oil pressure was present and not mess with the relay but did not feel like trying to get a port add a pressure switch cause I added closed cooling and my heat exchanger was in the way

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    not really a fan of the the auto charging relays cause they cause the good battery to charge the drained battery,

    Heck of a project for sure.

    Not sure which ones you've used that do this. The Blue Sea, BEP and Surepower units do not.



    I don't like the thought of having to flip a switch all the time to switch between batteries

    The DCP switch is ON when you hop in the boat and OFF when you leave. No switching while on the lake, no remembering to switch while on the lake.

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    I assume by BEP  you your talking about an auto voltage sensing relay that charges the main batteries first when the voltage comes up it just combines the banks which would allow for cross charge. the diode isolated systems work but you lose some voltage across the diode that is how i had done the batteries in my first boat the old supra that i restored


    I did use the DCP switch in mine so i can shut the batteries off when I'm not using the boat and to have the ability to combine if for some reason i would need to



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    5 hours ago, 2008_247lsv said:

    when the voltage comes up it just combines the banks which would allow for cross charge

    BEP as in BEP Marine. They call it a VSR, while Blue Sea Systems and others call them ACR. In the end, they all do about the same job. 

    As long as there is voltage above normal static (at rest) battery voltage, the ACR/VSR will close/combine, allowing that voltage to contribute to the other bank. As stated, this is voltage above normal battery voltage, so its alternator charge. In this scenario, its not the charged battery pouring into the undercharged battery, but rather the alternator's charge. 

    When there is no charge, or in other words voltage thats not above an at-rest battery, the ACR/VSR will open, isolating the main from the house. The ACR will not "cause" the charged battery to charge into the other one. In reality, the purpose of the ACR/VSR is to prevent just that. 

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