rssmithwick, your boat would have to be half sunk before water got into the motor from the exhaust. Just look at how high your risers are at the motor -- that's how far your boat woud have to be under water for it to backflush into the motor. If you're still worried about water getting into you motor buy some of those rubber flappers to give you a free flowing exhaust. If you're in fresh water make sure there aren't any muskrats near by -- they eat rubber like candy and you'll have to be buying new ones every month.