You might try the link again, Tortugas. It worked for me and the pdf displayed is the same as my owner's manual, which I think you'll find less than illuminating when it comes to trouble-shooting.
It sounds to me though that you're not getting input from either your transducer or your paddlewheel; you should have both for depth and log functions. I would check the wiring, paying particular attention to the ground wire (green) to ensure there are no breaks in it.
I understand your frustration and, if it is any consolation, this is the first I've heard of Silva (whoever they are!) being involved with the instruments. I was never able in the past to find any support of them from ComNav or Nexus either and it appears that they were a short-lived product sold exclusively through West Marine and beyond that knowledge there is a wide chasm of information I'm lacking, other than that I own one and it's still working.
goes into an expired craig's list page. You should try it. The nexus marine instrument looks like the Star Sea Data Log and Depth instrument but it is not exactly the same. It appears that Comnav was acquired by Silva which was acquired by Nexus. All I need to know is how to get data on the screen. I cannot be the only person trying to get this info.
I have to move a boat that has the Star Log and Depth Instrument installed. It will power on and it is connected to the transducer, but it does not show any data next to the labels that appear on the screen. I looked on the internet and the unit is now called a Silva Star Log and Depth Instrument. I do not know if ComNav Marine joined Silva or Nexus Marine or what, but I cannot find a manual in English under any of these companies that shows installation, operation and trouble shooting information. I would appreciate any help on this.