Sounds like it's running lean, maybe sucking air??
You should have 2 screws with springs on the top of the carb.
The right one is for the throttle stop.
The left is the air/fuel mix screw.
Turn it in slowly, remember the turns so you can reset it there.
Post the turns??Less than 1 turn?
Remove the screw and check the point and sides for damage.
Should be smooth.
Replace and set at 1 1/2 turn out.
Then start and run till warm.
Then turn the screw in 1/8th turn, wait 10 seconds for the fuel to burn at the new setting.
Continue to do this until the motor kicks, bucks, coughs, stalls.
Then back the screw out 1/2 turn.
That should get you close, repeat in the water in gear for final setting.
Some times the gaskets can go bad and allow air to be sucked in.
Can of starting fluid or carb cleaner.
Start the motor, spray the SF around the base of the carb and all around the intake side.
Any fuel coming back through the carb? Reeds make sure they are ok.
Your fuel pump is on the side of the carb, make sure the diaphragm is smooth and no holes.
