25 hp johnson starting on water

[big chuck]

fairly new to the boating world. bought a older 1976 starcraft for me and my son to fish and fix up. 25 hp 1977 johnson outboard will start right up in a tub of water at the house put it in a lake however and very hard to start if it will start at all. please if anyone has any info it would be greatly appriciated. i assume its a small issue since it will start and run great out of water.... thanks

 

[big chuck]

replaced plugs, wires fuel line when i first got it carb was recently rebuilt be previous owner runs fine when it runs yesterday put a half pint of seafoam in 2.5 to 3 gallon of fuel and run it in a tub of water and adjusted carb screw a bit run perfectly took it out to the lake this afternoon and run just fine no issues maybe clogged carb or out of adjustment either way seems to be fine thanks for your help and im sure ill be back before too long