90 HP Optimax serial# 1B803508 model# 1090D73HY
My boat had a D34M Optima battery last year when I got it, and I didn't have any trouble with it all last year but I wanted to upgrade to something with more capacity that met the requirements since the one I was using was technically undersized. I got Group 31 Commercial battery that's rated for 1000 CCA, used the marine terminals, put the motor leads on first and tightened everything down tight with lock nuts and the voltage often drops below 10 volts when cranking and I get a low voltage alarm, it dies the first few times I try to start it at the ramp then it does alright the rest of the day but I still get the low voltage beep when cranking and I can see my volt meter drop down below 10. I pulled the battery out and took it back to Advance and it tested just over 1000 CCA and over 1200 CA. My alternator is working fine showing between 13-14 volts on the gauge when running, I always have it fully charged with my on board charger before I go out, and I have a cutoff switch for all of my accessories to prevent any battery drain. I also took the battery connections apart, cleaned and tightened them at the motor and starter connections and it is still doing the same thing. What else could be the issue? It hasn't left me stranded yet, it always starts but I would like to figure out what the problem is.
https://shop.advanceautoparts.com/p/...p30/11968148-P