I have a nearly brand new group 27 deep cycle battery. The boat that I just bought needs a cranking battery. The deep cycle, according to the label has many more CCA than the minimum amount that 115 Yamaha calls for according to the owners manual. It also has a longer reserve than called for.

So I'm not a batteryologist. Is there some reason that a DC battery should not be used as a cranking battery, which will be charged by the boat motor?