depth

Hey so I just bought my first Sea-Doo, in fact my first powered boat of any type, and was trying to figure out the easiest way to get a working depth finder setup. I am wondering if it's possible to buy a used depth sounder for a 2004 supercharged 4-tec and install it on my 2004 GTX 155...

Instructions say to screw in to the same depth as plug, which is 19mm (3/4''). However, the only compression tester kits I see only specify 14mm thread. Am I to assume these will reach at least 19mm depth or should I get an adapter which specs list 19mm reach? I'm looking at this one since...

Does anyone have any experience with depth sounders. Bought a new Seadoo speedster but I'm too cheap to pay the $400 for the sea doo gauge cluster model. I was thinking about buying a Hawkeye transom mount. Anybody have an opinion on this??? Help?