battery switch questions

[dev6315]

Good Evening to all. I just purchased a 1990 250DA. This is an upgrade for my wife and I. While this is my 5th boat, I have never had a boat with a dual battery set up and switch. Can someone please give me a little info on this setup. Some do's and dont's. What if i need a jump or to charge the batteries? Are they in parallel or separate to eachother? They dont look to be hooked parallel to eachother, but I dont want to ruin the swtich. Any and all advice and insight is greatly wanted. Thanks in advance. Devin

 

[chuck1]

IMHO- When running keep switch on both.
When on the anchor (Running fridge/sounds)keep switch on one battery so you have the other to crank/start engine.