Twins, battery management

[kennharriet]

We sold our CD 22’ the Lochsa this spring and recently purchased a 2006 CD 25. It has twin 2017 Mercury 130 hp motors with dedicated batteries for each engine. What is the conventional wisdom on two start batteries plus house battery(s), vs one start battery plus house battery(s)? It currently has some house loads on the start batteries that I intend to move over to the house.

 

[thataway]

With your plans to move most of the load to the house battery: Go with one start, and two house batteries.

I have never seen a C Dory 25 with more than 200 hp. You must be looking for some speed records there. What is your top speed? Can the boat handle speeds over 35 mph? Now if it were a 255 Tom Cat, then I would look at top speed and batteries differently.

Thanks

 

[kennharriet]

Sheesh, I meant to say twin Merc 90’s. Also Bob you gave me good advice once before on wiring the windless to the start or house battery which I followed, but can’t remember what it was now?

 

[olekils]

Blue Sea Systems has some useful diagrams here: https://www.bluesea.com/resources/170/Battery_Management_Wiring_Schematics_for_Typical_Applications
I re-wired my boat and decided to have a house bank (2x6V AGM's) and dedicated starting batteries for each motor. Not super necessary but I like having each motor be as independent as possible. I just used automatic relays to manage the charging which has been working out well.