Hi Mark, No question is taboo. However, let me go back to "BOAT 101 - Basics". That course teaches you that the prime purpose of a hull is to separate you from the outside water, that wants to come up and grab you from below. Remember, the boat is just a hole in the water, and the water always wants to get back to a level surface, outside the boat, or inside, it really doesn't care which. The deck, cockpit, companionway bridge deck, companionway sliding hatch and the hatch boards, are all designed to keep water out of the inside of the boat. As long as water can't get inside and fill it up, the boat continues to float, and keeps your nose above water level. Therefore any holes drilled into the hull below the waterline, are looked at with deep suspicion by sailors. They are just waiting to trap you when you can least use the accident (Murphy's Law No. 1 Every Accident will Happen at the Most Inopportune Time Possible) The Pardey's are the extreme example of trying to minimize this potential accident exposure. They have no motor in their Bristol Channel cutter, so there is no propeller shaft and stuffing box to worry about; and I believe that they don't have a single through hull fitting on their boat. If you look in the WEST catalog, you will find them selling soft wooden taper plugs to be tied to through hull fittings so that in the event there is a through hull failure of any kind, the taper plug can be hammered into the hole to stop the flow of water into the inside of the hull. Your thought of putting the transducer on the outside of the hull and leading the transducer wire through a small hole through the hull sounds fine, but, ...... What would happen if, while sailing, the boat hits some stray piece of debris that then slides along the hull and shears off the transducer tearing the wire off as well? You have pulled the stopper out of the bottle, and depending on the size of your hole, the outside water will rapidly and happily find a new home, inside your floating home. Happiness to a sailor is as few through hull fittings or holes in the hull, as is humanly possible to achieve. Hal Roth and his wife Margaret, if I remember correctly got it down to 2: the sink / head drain, and the propeller shaft. Unless you want to reach the maximum achievable depths of your depth finder, my choice would be to mount it inside the hull using PlayDough, and retain maximum hull integrity. It becomes one less item that you have to worry about. Connie