Have not come across a log made by Smiths, is it quite old? What does it look like, is it a paddle wheel, small propellor or what? Would help if you could say what the boat was, somebody on here might have the same one.
Sounds like the log on my boat. It wasn't working so when I had the boat lifted out earlier this year I thought I'd have a look at its paddlewheel and try and fix it. There isn't one!
Took the log unit out of the dash and its only got a couple of spade connectors on the back of it (nowhere to attach a cable like on my previous log). Of the two wires attached, one went to the ignition switch the other to the back of the rev counter so can only assume it was meant to be working (guessing speed) by comparison to engine revs - still not working - think I'll buy a proper one to replace it.
Thanking everyone for the information and help but, I have found a company called Speedograph Richfield Ltd(located in Nottingham UK) who managed to help me with a new paddle wheel type water transducer it only cost me 23.50 GBP + Vat.