What is the difference between the x51 and the x51 pro? Can the speed sensor for the x58 and x51 be used on the pro? I see nothing in the online manual that indicates so. Overtons has them on sale for 59.99 - $5 if you use a code I found. $ 60 after shipping so for a cheap depth finder in the boat, can't go wrong. Just be nice if it could use the SP-X speed sensor.
