I have reviewed the OP's photos and find nothing at all amiss. I did look at the Airmar site and only found the "Owners Guide and Installation
Instructions", which only has drawings, but again I don't see anything there that is different. Perhaps you could take a copy of the photo
and add arrows or circles to show what you think is suspect? Also, upload the brochure as it will have the dimensions for comparison to newer products.
There are 2 listings on ebay.ca for the paddlewheel/o-ring kit at about $50cad. I would buy one of these unless there was a decision to replace.
If the OP wants to replace then those dimensions are critical. It might be possible to use the existing thru-hull but it would have to be checked closely. A generic Airmar tri-ducer should work
well by splicing into the existing cable, or better see if there is a RM version with the right plug
. Personally if there is a decision to replace I would install a "smart" transducer
, either NMEA 0183
or 2000 with an appropriate head
. The world is moving on...