I bought a 18' beavertail w 35 hp vanguard (b-s) motor.
While bottom painting the boat i had the motor laid on its
side for a week. Reinstalled and now motor runs very rough
under load but fine with no load. Any thoughts?

Check ur spark plugs and ur carb

Thanks I'll try this weekend

I wanted to follow up on the vanguard engine issues in case others had the same problems. Because the engine was on its side for a week oil Leaked into the right cylinder. When trying to start the oil locked the engine also bending a push rod in the process. I found the problem by starting the motor pulling the spark plug wire on right side engine still kept on running. Replaced right side wire then pulled left side plug wire the engined died. So only the left side was working. Removed spark plugs and grounded to engine. Both spark plugs looked good which points to carb or mechanical. Pulled the valve cover on right and there it was the bent push rod. Replaced rod set lash to .005. Replaced cover and had all 35 HP back on tap. Just wanted to help anyone else having a simmilar issue.

Thanks for the update....Duckdon