RE: My 6V House Batts
The best is to use deep cycles for the house and starts for starting.
Almost no amps are used for most starting , and should someone crank too long , the starts will stop giving juice , as the plates get covered with bubbles. Wait 5-10 min and you can have another attempt or two. Good safety feature.
However I have been on boats with NO start batt set. BUT it was a sail boat with tiny 35hp engine and HUGE house set.
The voltage for starting depends on plate surface area , where starts excel, but with close to 1/4 ton of house batts , the surface area of the deep cycle batts was enough.
Always best to use a hammer on a nail , rather than the hydrometer!
Starts to start , 6v golf carts for the house, DONE.