not likely, the damage will occur when water is mixed in with the lower unit oil. that is why it gets changed every fall. i fish seneca in the winter as i am laid off. i never wintrize my motor, i use it maybe 6 t0 10 times per winter. the small amount ofwater that is in the motor will drain freeze and thaw and drain.i have never had any problems with anything breaking. you could cover the prop with a bag to stop water from entering thru the exhaust hub, thats probably where the water you saw came from. tight lines. by the way, i should add that my mercury is a two stroke but i am pretty sure the water will not destroy your motor. the motor will most likely have freeze plugs anyway.