One speedo or 2?
There are of course adjuster buttons somewhere on your boat as well for the speedos. This could vary but the whole point of the medallions was that airguide speedos were NLA and they needed two adjustable speedometers for tournament boats to be approved. So most of these boats have rocker switches somewhere on the boat.
This means there are two things you need to find, A - where are the rocker switches find them and tap the up button a number of times and see if your gauge comes on. And B: in this application usually there were two speedos one got pulled to install the PP, but there should be two speedos and technically they should both be separately adjustable with rocker switches, so there is probably a second wiring harness loom behind the dash for the speedo. If so I would switch it over and verify.