I have bunk boards on all of my boats including a 18ft ranger bass boat with 150. That thing was impossible to push off unless it was 3/4 floating. I found a product called Liquid Bunk Roller and sprayed it on the bunks. I went to launch the boat the next time and if it was not for the safety strap it would have ended up on the ground. I can launch it wet or dry with just a light push it is crazy how well this product works. I replaced my tie downs with a seatbelt type strapping system and a chain just to make me comfortable about how easily it slides.
Art