F250/LF250 / 2007 Isolator lead

[Freddy]

Boat.net
A few weeks ago you forwarded info to me aboat the isolator lead. I want to use this lead to charge a 3rd battery that I am going to install. Currently I have twin engines and 2 batterries. In the near future I will be installing a 4th battery also so my questions pertain to both engines. Currently the isolator lead has been extended and connected to the positive terminal of the engine crank battery. Since the crank battery is charged by the engine crank lead , why is this connected like this? Also can I disconnect the isolator lead from the crank battery and hook it to the 3rd battery?

[boats.net]

Yes move the isolator lead to 3rd battery, it would need a jumper wire between battery grounds to tie negative together.

[Freddy]

Thank you, but why did the factory connect it to the cranking battery per Yamaha's direction?

[boats.net]

Not sure, maybe that was the only battery installed at that time.

[COJones]

Boat.net
A few weeks ago you forwarded info to me aboat the isolator lead. I want to use this lead to charge a 3rd battery that I am going to install. Currently I have twin engines and 2 batterries. In the near future I will be installing a 4th battery also so my questions pertain to both engines. Currently the isolator lead has been extended and connected to the positive terminal of the engine crank battery. Since the crank battery is charged by the engine crank lead , why is this connected like this? Also can I disconnect the isolator lead from the crank battery and hook it to the 3rd battery?

Freddy,
I have a 3 battery set-up on twin 2004 300 HPDIs and currently have my strb engine charging its starting battery and the house (through the aux output) while the port engine charges its own battery (not using the aux output).

Wanting to be able to charge the house battery independent of which engine was running, I connected both port and strb aux outputs to the 1 house battery but ran into a problem. Depending on which engine I key-up and start first the second engine to key-up and start will not charge correctly at lower speeds. I don't understand why hooking-up both aux outputs to a single battery causes this concern and would really like for someone to either have experienced this before and/or could explain what I'm seeing. Any feedback would be helpful. I really would like to not have to manage the house battery charge while *****ing on 1 engine for example. BTW: The local Yamaha tech really couldn't explain it either but did say that it may have something to do with how the yamaha smart/computer regulator manages/senses the charging of the aux battery.
Thanks,
David

[boats.net]

If the isolator senses high voltage from battery it will not charge, if first engine is charging 13+ volts the second thinks battery is charged.

[COJones]

So why would it effect the charging of both batteries (i.e. starting and house)if only the house battery (which would be hooked-up to the running engine) is the one which doesn't need the charger? Shouldn't the house battery charge independently from the starting battery? I thought the purpose of an isolator was so that you could do just what I have described above. I'm completely confuse. Thanks for your reply but I still would like some additional clarification if possible. Could I call Yamaha and discuss this with someone?
Thanks agian,
David

[boats.net]

Not sure the charging system would need to be tested. Yamaha does not recommend connecting isolators from 2 engines to one battery on that motor, maybe thats why.