I have a 13ft. inflatable with a old 20hp outboard. My problem is when I start to gain speed a spray of water comes up from behind the transom; the faster I go the more the water sprays. The water will come over the transom and into the boat. I took a look and it seems that the water is hitting the lower of the outboard and spraying up in a fan. Anyone have any ideas as to how I can fix it?