a m8t wants to buy a 20hp the model no: 20cm 6e9 s 01194 on the transom , now he says the exhaust coming out through the prop , & i told him they never made a 20hp with that serial no in the year 1994 , i have an impression something has been swopped , the ? what year did they change the exhaust flow from coming through the prop to top of prop , thks 