Looking at the NJ MVC site, apparently boats 12ft or less do not need to be titled, but do need to be registered if they have a motor (electric or gas.)
http://www.state.nj.us/mvc/Vehicle/Boats.htm
http://www.state.nj.us/mvc/Vehicle/VehicleBoats.htm
Looks like Walter was wrong, its probably only moderately painful. But like any MVC transaction, plan on at least 2 visits.
Either way, I think yous guys will need some sort of notarized affidavit of transfer of ownership from whomever you got the boats from.