Not too bad, as the main electrical panel is only about a foot above the ducer I took the precaution of wrapping a garbage bag around it. Pulled the old unit out with my left hand had the new one in my right, once it goes into the opening the O-ring stops the water flow so, I'm thinking a quart of water came in.Glad you got it fixed. Did you do the installation with the boat in the water? If so what kind of water flow did you get?