engine stalls

[rosietheboxer]

i have a mercury 3.0liter i/o engine on my bowrider. When i start from a cold start, the engine turns over nicely in "out of gear" (3/4 throttle) position. After keeping it in this position for 10 minutes or so, i'll bring it back to neutral. When I put it in gear , i hear the engine rev up. it revs and then dies. It is using the same gas (which had stabilizer) from last year. THis is the first time I am taking it out this year. Is it as simple as i fresh gas or does it soud like something else?