A few issues that I can think of outside of the concerns of being drunk...
Foam. The boat is going to shake the keg a lot.
Temp control. Too warm, and you get foam.
CO2 storage. Even the smaller tanks are going to take space
On land my keggerator uses a full sized frig, large cO2 tank and a constantly stable platform i.e. my gagarge.
What i would like to know is what size keg and cO2 tank would you like to use?
Also, kegs or the beer rather tend not to respond well to viberation.
All in all i love your idea! So the first consern is were will your keg be cooled. Other than that power and keg lines can go anywhere.
So space and movement are your big concerns.