This past weekend, I put my 1979 Renken Tri-hull with a electronic shift Johnson 85 hp outboard in the water for the first time in over 10 years. It was my summer project and on land, I was able to get it started and have the propeller turn forward but not backwards. I put it in the water too make sure it floats and to hopefully take it for a spin. I got it in the water and starting it took a good 10 minutes, but I finally got it fired up and put it in forward gear and went nowhere. I saw the water churning behind the boat, but I wasn't moving. Any help to why my boat won't move?