2007 Mercury 2.5hp 4-stoke - Idle and high RPM questions

[kenyu73]

I just bought this motor used. The carb was gunked from sitting (ethanol gunk), but I got her cleaned out and the engine running. However, while running on a post and the lower unit in a 5gal bucket of water, the motor would not stay running while the twist throttle was in "start" or even a tad above start. Is this normal or should it idle with the throttle all the way down? It does run continuously at about 10% throttle or higher... etc...

Also, when I give it say about 75% throttle or higher, its runs bad like the fuel/air mixture is off....

Will this run better in gear while running her on the dinghy in the lake?

Thanks for any advice!