electrical upgrade / adding battery switch
 

hello everybody!

im doing some electrical upgrades to my 1990 mariah. The boat doesn't have a main circuit panel just push button resets kind of like a circuit breaker you just have to push to reset instead of replacing a fuse. im adding a second battery , a battery switch - a blue sea switch that has off, 1, 2 and 1plus 2. I also want to add a main circuit breaker, im just not 100 percent sure how big the breaker needs to be amperage wise. The boat doesn't have much as far as power usage, just lights, stereo, starter and cabin fan. im thinking a 100 amp main breaker should be more then enough, i want to prevent a catastrophic short circuit from happening in case a individual circuit breaker fails. also my stereo amp has its own fused 60 amp circuit so this will not be factored into the main circuit breaker. what is anyone opinion as far as amperage on the circuit or any other thoughts , suggestions in regards to electrical upgrade. some point in the future i want to add a on board charger so when im plugged into shore power the battery will charge.

thank you for the advice!