I have 2 motors, 150, and a 15 kicker. I tried the red washers on one and a black washer on another and they were snugges down pretty tight. Just curious about the vibration.Maybe those red fiber washers compress a bit and could use a re-tightening occasionally.....although I personally have never had any issues with these drain screws getting loose. I do tighten them down pretty darn good with my gorilla screwdriver.
Good information, I'll give it a try. Thank you.