after almost 10 years i decided to install a dual battery set up in my 24sslx . the switch has battery 1, both, 2, off. when starting the boat do i keep the switch on both to charge both batteries and when we get to a cove turn the switch to battery 1 to use axillary power ? then when we leave switch to battery 2 to start the engine ? I wired the system to Benningtons drawing 4069 dual. I understand not to turn the switch while the engine is running, so the only way to charge battery 1 is to run in switch both. also i have a Yamaha 115hp engine will the alternator be able to charge both batteries at the same time ?