My Sunny had two switches but for some reason even when on bank 2 my starter battery would drain. I took one switch out and now I'm not getting stranded anymore.

Thanks for the Perko diagram. Anyway I usually put them on both....
And my Port is also house.

I leave the port/house to battery 2, its a 27 group.

and the starbord on batt 1 (24 group). that way IF i kill batt 2 playing radio, frig,what ever, i still have batt 1 to start off of. and this keeps each motor charging one battery. I also will swap up which battery i use on the each motor to kinda of cycle the batterys that get drained.

I want to add a 4th battery. so if i seleect batt 2-- its really 2 grup 27 tied together. that way i have a BIG house battery, a spare battery on starboard motor, and the genny batt (3rd battery is only for my genny)

I have been boating with two or more batteries for 30 years.

1) In single engine setups I never run a battery switch on BOTH unless one or both batteries were weak. Then only to charge the weaker one or find out it won't take a charge. I switch batteries a few times during the outing. If during the day one batt gets weak from the stereo, age or WTF, I fire up the engine on the other one and go home. Never a problem. No, not one.

2) In 2 batt/2 engine setups I run each engine on its own battery all the time. I never run this situation on both. If during the day one batt gets weak from the stereo, age or WTF, I fire up the engines on the other one and go home. Never a problem. No, not one.

What would be the best way to run 4 batteries? One for each engine (3) and one for lighting/sound?

Multiple battery setups are a problem in boats and using more than two usually requires a battery isolator or charge relay. This may be more complex than you want to get. I don't know of any three way battery switches, only two. I did know one stereo geek with a huge stereo (16 speakers and 3 subs) that paralleled two blue top Optima batteries on each connection of a two battery switch to run 4 batteries, two for each engine. Was out with him several times one summer and he never had a problem I know of. Once he did run his motors for a while to recharge the batteries.

Correct 3 batteries in parallel on the one side and only one on the other swich.. You can jsut leave it switched to battery # 2 on both and it excludes the other bank. meaning the stereo runs of the side w 3 batterie.. Only when you click it to all you get all 4.. Othwerwise the one battery is only drawn to start and run a trim pump or 2 and other key on related stuff

Yep these guys are talking the same language.

I personally want 4 batterys in this set up

bat 1= one (used for starborad motor only)
bat 2= 2 batterys in parallel (used for house and port motor)
Both = all 3 batterys tied together.

and a 4th for my genny.


I do have a buddy with 4 batterys, 2 tied to posision1, and 2 tied to posision 2. and both being all 4.

I have 3 outboard engines though....and I would like to have 1 battery dedicated to each engine....maybe I could use two switches with 2 batteries on each? Sorry I am still slightly confused.

This it?