I epoxied it just right of where the drive shaft goes through the hull. I read online some tricks to determine best location. Hang over side of boat to get accurate depth then put in a plastic bag of water to move around in hull of boat to determine location. Must put away from supports, fins, shaft, etc. When you find best place put Vaseline on bottom of transponder and try to duck tape in place. This way you can drive boat to make sure no wash affects it. I then let hull dry good and used 2 part slow cure epoxy purchased from Hawkeye. Hope that helps.