water in the fuel/carb can do the same all it takes is a few drops in the carb and it can do many diffrent things an with todays gas.Im gona figure ur tank is under the floor an with the weather we have now with a little water under the empty to half full tank it will or can rain in ur tank especialy if it was sitting for any amount of time

im new in this subject but does it shutdown or die off till u lift a little?
i own a boat repair shop an i work on all jet,i/o,vdrive an so on but again if u need any more or cant get it let me know