I have a 20 HP 2015 Nissan outboard motor on my flat bottom and recently it has been running strange. It acts like it is still choked when put in the forward drive position, maxing out at 7 MPH, when i usually run about 21 MPH. If I continuously run it like this it will eventually start trying to run normally. You can hear it when the motor starts firing correctly. The odd thing is though, is that the motor revs and runs correctly when in the neutral or reverse positions. Yesterday i went out and it didn't run right the whole time. I've taken the cowling off and every thing mechanical that is visible looks to be working in order: the throttle/cable, the choke, the mechanism to switch from F-N-R. It is almost sounds like something is stuck in the carburetor but that doesn't seem possible to me if it revs and runs right in reverse. However, i am not a boat mechanic. I have tried changing my gas, thinking maybe condensation or water had gotten in, but i've ran a whole tank of 93 through with seafoam. It had seemed like it would get better as the motor warmed up, but it seems to be getting worse as i could never get going on the lake yesterday. Any troubleshooting or pointers would be greatly appreciated. I've just started trying to research it today and figured the forum is a good place to start!

Have you checked the plugs?

That's what I suggested prior to your post, guess he didn't want to here it, cause it was deleted...Lawton