I installed a backup Hawk Eye depth finder about 8 years ago, using vaseline to locate a spot it would read out. Tried about a dozen locations before I found an area that consistently gave readings. It is about 18" starboard of the keel, under a lazarette. Closer than that to the keel seemed to be the problem, not sure why. Siliconed it in after settling on a location, works great. Keep looking for the sweet spot.