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Correct/optimal battery spec for Honda BF75 outboard?

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  • Correct/optimal battery spec for Honda BF75 outboard?


    I'll soon be fitting the outboard to my boat and will need to get a new battery for it.

    I've got the battery still from my old one and it is in good shape but that was a 50hp yam and the battery is a little on the small side for my liking even though it has started the honda no problem so far. It's a pretty old battery too, so I don't want to take chances with such things.

    What would be the correct spec battery in terms of AH and CCA for the honda? It's a 1996 model BF75.

    I presume also that there's no issue at all in getting something above the necessary spec in respect of either cranking amps or amp hours? Ideally I'd have one with more amp hours I think, to give more margin for errors etc. Just in case.

    The other thing is that I would then be wanting to use the old battery for running on board electrics while the engine is not running.

    I've had a split charge system in my discovery before where it used a relay wired to one of the alternator wires to control the connection/separation between the two batteries, but I'm not sure how ideally this would be set up for the likes of the honda? I know you can get rotary switches that are like isolators, so should I just get one of those to disconnect the second battery from the engine when not running, and wire all the electrics to the 2nd battery?

    There's a solar panel to chuck into the equation as well, which will be plugged in when the boat is on the drive, to keep the 2 batteries gently topped up.

    Many thanks!

  • #2
    Battery requirements are 70AH 550 CCA
    Better to install a battery isolator to charge both batteries.
    Honda Outboard Parts


    • #3
      That's great thankyou

      I've just bought a rotary isolator switch which does "1, 2, both, off" which should be ideal I think.

      Am I right in thinking I need a different type of battery for the starting one to the one running the electrics? Ie one deep cycle and the other not?


      • #4
        Yes two different batteries would optimize your electronics, be sure to keep them separated while in use, or you will kill your starting battery. Deep cycle is good for the electronics.
        Honda Outboard Parts