'68 Johnson 20 HP- Starts then dies

Motor has set up for about 4-5 years. Got it out 2 weeks ago and using a barrel full of water it started up after cleaning spark plugs and ran good. I started it up several times and I was surprised how easy it started. Today we put it in to go duck hunting and it starrted on the 2nd pull, ran about 20 yards and died. Couldn't get it started in about 20 minutes of pullin on it. Took it home.
It will start and run a couple of seconds then die and will run when spraying starter fluid in it.

I'm thinking maybe to carb needs re-building again, maybe float is cracked.

Any ideas????