Serious Starting/Running problems for 1987 yamaha 150hp!

Had no spark last September 2009. Mechanic replaced: Stator, timer base, fuel pump, & regulator. Boat stayed in water all winter in Freeport, NY & was never winterized. Motor started & ran rough. Made 2 trips this whole 2010 season. Recently, tried starting it by removing carbuerator air shroud & spraying carb cleaner into all 6 carbs. Motor starts up, revs high, sputters, & then shuts off. Do you think the carbs need to be rebuilt ? (It has never been done)

Do a compression test first make sure all cylinders are within 15 PSI of each other,if there not then its not a carb issue.If they all check out,I would.defiantly rebuild the carbs.being that it sat for some time without running.Carbs are more likely to get stopped up not running it often, then if you were running it all the time.Majority of the time blown motors are cause buy carb problems.So then you should not have to worry about them for a while. I'd almost guarantee it fixes you hard starting and rough runnning. Let us no how it turns out and go from there.Good Luck

John: Hope you see this,would like to talk to you. 602-705-9446. thanks, Kim Moffo