jhonson 1985 150 hp idle?

[liorlilah]

Hello evryon.
i just got an jhonson 1985 150 hp
rebuild carbs, change all fuel lines, and coils.
the engine start great and idle at around 1100rpm, and after couple minute it just jump by itself to 2500-3000rpm, after a while it go back to normal and so on.
any ideas?
thank you

[boats.net]

Sounds like you have a vacuum leak somewhere. Spray water around the engine and carburetor base, see if it boggs down, this should show you where your leak is.