runs great in barrel

I have an Evinrude, Fastwin serial #18603C-E02714. I'm not sure what year it is. It starts, runs, and idles just fine in a barrel at home. I can put it in gear, forward or reverse and it will run great, until all the water swishes out of the barrel from the propellor spinning so fast. Basically it runs perfect from top to bottom at home. When I get it on the water it will start fine, but when I put it in gear it wont go more than idle speed, hence the name slow floater. The motor doesn't sound like it is bogging down. It sounds like it just doesn't get over idle speed. Both plugs are firing great, the bubble stays tight, the throttle is working correctly, and I've cleaned the carb twice thoroughly to a spotless shine.This has happened exacly seven times, and each time I come straight home, put it in the barrel, and it runs perfectly.This thing is causing me to lose my religion and some hair. PLEASE SOMEBODY HELP ME!!!!!!!!!!!!!! Thanks, Slow Floater

Re: runs great in barrel

it's an 1966 18hp rude. the 2 things you did not mention. compression test, and the size and type boat it's on. if you haven't check the compression as they can run great with low compression, until you put them under strain.