I installed a new electrical system on my 21 foot boat recently. The set up I decided to go with was a Group 24 80AH Deep Cyle AGM, 20 watt solar panel, *7 amp charge controller and 250 watt inverter. The set up seems to work nicely for my needs.
It would also make sense to replace all interior and exterior lights, with LED.
First thing is to analyze your electrical usage on the boat. I assume on a 22' boat the power usage will not be great but that depends. Will you be running a stereo, cabin or navigation lights, GPS, plug in cooler? Will you have a motor that is electric start?
Second, due to the size and space restrictions of the boat it will be impractical to install a really large battery bank. So, assuming you won't have an electric start engine and not too many of the options mentioned above I would look for a 12V, Marine deep cycle battery that will fit in the battery space that is probably on the boat.
Before anyone jumps in to yell, that battery will not be a true deep cycle like a Trojan T105 but I don't know of any true deep cycle batteries in the size you will fit in a 22' boat so that will be your best option.