Old fuel will create some gel,it wasn't water. It was meant as an example,dirt will do the same thing as I don't figure your fuel is old enough to gel. It could be someting as simple as when they had the motor apart the fuel lines were diconnected,when one of the rubber lines was reconnected a small peice of the rubber line was broken off on the inside of the connection and made it's way into the carb. It's a cheap and simple check to ,if nothing else rule it out.
I don't have any experince with inboards but have a fair bit of experience with older cars and trucks an alot of carb problems come down to a little bit of dirt in the carb. Just trying to help!