Johnson won't run in gear

[AAC]

I recently bought a 1997 cajun with a 1997 Johnson Faststrike 150hp, boat sat for about 9 months before I bought it. When I initially took it out it worked fine the first couple times, then it went downhill. I would be able to get out to the lake and run it but when I tried to move again it would start fine but when I put it in gear it just bogged down and died about 15 times before I could finally get it in gear. Started happening more often so I took it to mechanic and had primer bulb replaced and carbs rebuilt. Went out to lake again and couldn't get it off the trailer. Starts up fine but I let it idle for a few minutes and it just coughed a few times and just shut off. When I try to put it in gear it just loses RPMs, boggs down and shuts off. Idle got worse, it would start fine but then gradually lose RPMs again before it got low enough, coughed and shut off. I am a novice with outboards, any ideas what the problem could be?