I have a 3YM30 in our Hunter. Installed a group 27 start battery, 600 CCA, 750 MCA, on an echo charger and 2 Group 27 as house bank on a 1,2, both switch. Typically I leave it on the house bank and start the engine from that bank. I only use the engine start battery if I draw down the house bank too far. It's happened a couple of times, but have the reserve engine battery as back-up.