My wife got me a new toy for x-mas this year, a Garmin 546S. I will be installing this on my 21' Scatcraft. This is an old deep-V cuddy. I'm looking for a good transom mount transducer. From what I have found I should go with the P-66, tri-ducer. I dont necessarily need the speed, as I can moniter speed from the gps. My primary use is for fishing in the LI Sound, in depths ranging 6'-150'. I before I purchase the P66, I wanted to see what others think. How is the accuracy under load? I'm not a speed demon, but would like accurate readings at cruise around 20mph. ANy thoughts?