Really not enough information to make any accurate diagnosis. Have you followed the basic gas engine
trouble shooting beyond what you mentioned? Gas engine
takes three things to run: compression
and spark, the last two of course must be there at the correct time.
WARNING!!!! Be very careful testing the fuel and spark. Spilling gas or fumes in a boat could make an explosive situation. Checking spark after that could turn the situation into a big boom.
: how long had the engine been sitting, years? Any chance the rings are frozen up or valves stuck open so you aren't getting any compression?
Fuel. It's getting fuel but how far down the line? Just to the carb or all the way to the cylinder?
Spark. Do you see spark on the plugs when you turn over the engine.