Hi,
The answer lies in your last paragraph - its not suitable for this intended use, as you need to remove it from the boat to charge.
Why? Well, the red/black cable are the connectors to load, and also the re charging connectors. The 3 fine wires are for balance charging, these connect to a dedicated lipo charger - no, you cant use your standard charger, they need a specific lipo charger.
And, they should be charged under observation for safety, they have been known to fail VERY spectacularly - look on u tube!
For info, the rest of your questions:
25c = discharge max current is 25 x capacity, in this case 1200ma (1.2a)
2s1p = 2 cells wired to give 7.4 v. Each cell gives 3.7 v under load (hence 7.4v) and have to be charged so that they are equal (balanced) voltage otherwise there could be a risk of a higher charged cell discharging into the lower cell which can be fatal for the battery.
My opinion? For this application, stick with the gell cell.
Ian