Main Battery wiring thoughts.

Got an 88 model evinrude 30 that was originally a pull start model. Upgraded to electric start but did not have an alternator on it. Putting an alternator on it now, and my question is the best way to wire the batteries. I plan on having main battery and another deep cycle. Going to put a battery switch on it allowing me to charge both while running or use both in an emergency, or isolate them during use. Only electronics will be nav lights, lightbar, depthfinder, and a bluetooth direct amp. Anything I am missing or not thinking clearly about?

I would use the alternator to only charge the cranking battery. Most boats don't run enough on the water to charge the cranking battery back to what the fish finder pulled it down to. I know mine doesn't. A short, cheap set of jumper cables would let you crank the boat with your trolling battery in an emergency situation without having to unhook things.

Do you already have the switch? Them things are expensive to have one rated to pull starting current and last. Just use deep cycle for everything else and do what fur said. I've got a little solar charger that helps keep a little charge on deep cycle battery during the day. Or you could buy one of the 2 bank chargers and charge both while your running.

Do not have the switch. Found perko’s rated for continuous 250 amps for about 35 bucks. Not necessary for my setup but would be nice to be able to easily configure what battery is on.

Just remember once you put a charged battery in parallel with a discharged battery they are going to try and equalize. If you can still pull start it that might not worry you too much.

That motor does not have an alternator does it? Regulator/rectifier is just made to "maintain" a battery at 12.6-12.8v.

He said he was putting an alternator on it. "Maintain" just means charge. Battery doesn't care if it is from a rectifier or an alternator.

No it doesn't have anything on it now but will. You make a good point about the batteries in parallel. The only time I would foresee me running it like that would be in a situation to try to get some juice from the motor in a pinch. The switch is likely overboard but one of the problems now is the batteries are exposed and the mess of wires and terminals is awful about corrosion. I am looking to get the wiring cleaned up and get the batteries in an area where they are a little more protected.

Just cover posts in grease!

Ha in the current setup that would do nothing but piss me off as I am trying to take battery connections off and on.