This transom mount stainless steel transducer spray deflector can solve a lot of your problems. It allows you to run the transducer deeper in the water to get a better reading but you don't have to be worried about the resulting salt spray getting sucked into your engine. It is 150mm wide at its widest point and is 200mm long.
This unit is the same dimensions as the one above however the mounting tabs are bent down so it can fit on a smaller transducer bracket. This is the one you should get for almost all Quintrex and Stacer boats (and any other brand of alloy boat) that has a welded on transducer bracket. It is 150mm wide at its widest point and is 200mm long.