I'd just be guessing but 550-600 CCA would do it. BUT -- when it comes to battereis, you cannot have too much capacity. Install the largest capacity battery you have room for and forget about it. The difference in price is negligible. You can only go too small -- you can't go too big.
450 minimum 550 would be good. Go for "Reserve Capacity" or "Amp Hours" over CCA. Which normally means a larger physical sized battery.<br />People get worked up over CCA but on a boat it's one of the less important numbers.
