Fill All Holes in the part. Water Inlet and Water Exit ports or what have you. By Surface By Boundary
Then once you have all the holes covered with a surface
Go to Delete Right Click and choose surface chain options
Then Click auto chain. Then select a external surface. This will select all of the surfaces on the outside of the part. (You may have to right click and click on highlight selection )If the entire part gets selected you have free surfaces or you have not filled all the holes in.