So you have an R28 too? What year? I got mine as my first boat about a year ago and have it in Annapolis. '76.
I'm having the same problem in figuring out what all is original and what's been changed. The previous owner used it purely as a racing boat and had retooled it as such. The inboard has been taken out, much to my dismay, and replaced with a 8hp outboard.
I'm going out this weekend and will take a look at the Transducer gear. I'm not sure what it is, but I discovered it finally in the front V berth, but on the port side. The starboard side has the water speed indicator. Neither work well.