My boat is set up exactly the same way, except that both main engine and genset on my boat are 12v, so I can't jump the engine directly with the 24v house bank. IIRC, the Oysters with Perkins
engines have 24 volt starters.
Of course you could get rid of one of those banks, but why would you bother if it's already there? This redundancy is great.
I have had to jump my genset with the engine start battery and was really glad that these two batteries are adjacent in the same battery box
. In an emergency
(say, both engine and genset start batts dead), I could take one battery out of my house bank and use that to start the engine.
One time I arrived on board after being off for six weeks to find every battery on board dead. The house batts died because I had left the batts unisolated -- I had just installed a wind generator
and thought that they would keep up with the small drain. My secondary bilge
pumps are not directly wired so I though I could just leave them on. Big mistake!
Why the engine and generator
start batteries were dead also I have no idea to this day. Bizarre. It was a cold, dark night when I came on board my totally dark and cold boat with all dead batteries after a long flight. In desperation, I took the tiny start battery out of my dinghy
(!), the only non-dead battery on board, and used that to jump the main engine. Incredibly, the little bit of extra power did it, and I got my Yanmar
started, and then set about gradually bringing the ship back to life.
Moral of the story -- sometimes that little bit of extra redundancy may save your azz.