well im a master electrician but no expert on dc 12 volt but am willing to give advice and or stop by to help .I am very busy but do have fridays off , wouldnt mind helping no charge to anyone on the board email me thanks jeff

Jeff....well since you offered...My current set up / wiring is simple but its about to change and I have to say after a lot of reading I'm uncertain as to how exactly to pull this off...

First, what I have: Honda BF90 with charging system wired direct to main (house) / cranking battery. All "house" electrical (that installed by Alumacraft) runs off the main battery, a bunch of "house" things wired up to the fuse box by the console and then several things that are wired direct to the battery including two (2) canon Mag 10 riggers. Even though I did some of it myself, I forget if I have the GPS/Sonar (Lowrance LMS 337c DF) wired direct to the battery or from the fuse box. I also have an auxiliary battery compartment with two deep cycle marine batteries. Currently they are hooked up for 12 v and only power the factory plug outlets for an infrequently used Minn trolling motor.

What I'm adding: '03 Honda 9.9 4 stroke with high output charging (6A idle, 12A 3,000 rpm). I'll be using this extensively for trolling not just emergency and so I need this to be an alternate "main" as far as charging goes.

Also adding VHF (want to run off one or both auxiliary batteries to keep it from causing drop outs on the GPS/sonar), Simrad AP-14 autopilot (was going to wire direct to main?) and possibly the Troll Master for the kicker (very low draw, wired to 2A circuit in fuse box powered by main).

Here's what I'd like to be able to do but don't know how...I worry that I could damage the charging system of the "other" motor not in use (or other electronics) if its not done very carefully and "right." I'd like to be able to use either motor (or both?) to charge either (a) the one main battery or (b) two auxiliary deep cycle batteries or ideally (c) both automatically. It would seem simple to wire a manual only system with 2-3 switch boxes, but it would a require sharp attention to detail and protocols to use a manual only system (i.e., no "auto" charging of both batterry systems). I've read that ideally its better to have an "auto" charging system that first tops off the main / crank battery and then automatically charges the other batteries and then auto switches back and forth to keep them all topped off. However, I've also read about problems with wiring this up -- like frying expensive electronics in the motors. The manual system is not foolproof either, as a failure to follow exact protocols for setting the switches (and when) could also lead to frying something.

One last thing, it also might be a leap forward to move the house and all the electronics that are currently wired direct to the main batt to a switch box that would allow the house and other electronics to be run from either the main or auxilliary batteries.

Sorry this took so long but you asked! Also, I'm down here in NY so this might be a real test for you to try and guide a novice remotely, but I'd pay attention if you tried.

-Eric

wow , well let me see whats available for auto charging and do a little research im sure we can manually come up with a series of switches and a protocol to make it happen but , I would like to do it the best and simplest way for durability .and ease of use . Do you have a two battery switch installed now ? if so what type make and model and anything else you can think of would be great .thanks jeff

Jeff - no, I don't have a switch installed (yet). Apparently you can't just use automotive electronics. For marine applications its important to have intrinsically safe / spark arrest rated electric gear. I've heard guys have had fires from using auto or household electric gear on boats.

I'm treading water. My Honda mechanic is searching for solutions but its tricky stuff to do what I want and to do it right and safely.

-Eric