Re: 1999 Johnson 25hp
I assume you mean that you must keep the choke closed. A open choke is just that (not actuated).
This would indicate that you either have a bad fuel/air leak at some point between the fuel pump and the fuel supply (fuel pump drawing air) OR the carburetor is fouled and requires cleaning/rebuilding (most likely).
Also..... DO NOT rev the engine when in neutral. A engine running on half of its cylinders can be raced in neutral as there is no back pressure/drag/etc BUT you could encounter a runaway engine that would simply race away even with the throttle closed. By the time you figured out a way to stop it, connecting rods would be flying out the side of the crankcase.