I had the same problem. If this is an OPTI, pull the engine cover. On the right side is a silver cover box, at the bottom is a black small hose connected to to male ends at the bottom of the box. This is your gas vaporizing unit. Disconnect the bottom hose at one end, turn the set screw which opens a passage way for gas to drain out of the gas vaporizer chamber. Drain it into a cup and check for water. On my 200 Opti the water sensor is on the left chamber and this is what kept setting off my alarm. Check both sides.When done pump your tank bulb to refill the chambers.Note I was told that if your gas has a lot of ethenol in it, it tends to collect water if it sits for any period of time. The ethonal gas is what was causing my problem.
