9.9 2003 Mercury

I have 2003 9.9 2 stroke merc that starts very easy every time in the shop but when I go fishing , take it off the trailer it starts and runs fine wot,idles great. Now sometimes after I have fished a bank for maber 200 hundred yds it might start right up but sounds weak .When it does this it bogs down and quits . Then I have to choke it to get to wot. Sometimes it starts and runs fine.I have hade the carb and cleaned . Can wave action cause this? BTW when I got home today the fuel boal was half full, I suppose from bumpy roads.It is on a 16ft bass tracker pan fisher . Thanks.