Navman transom paddle wheel

thingiverse

I've got a Navman MULTI 3100 on my boat that tracks speed, distance, and depth. The transducer is mounted at the stern, the transom, where it's supposed to be. At first, the depth gauge was working fine but the speed reading was stuck at zero. Upon closer inspection of the transducer, I noticed something missing - the paddle wheel. The spindle was still there, but no paddle wheel in sight. I did a quick Google search and discovered that Navman or North Star is no longer trading, which explains why all their spare parts are gone - including the paddle wheel. After some digging, I found it might be part number 46302 or AA002078. It has six paddles, measures 27mm across and 10mm wide, with a 9.5mm hole for a plastic insert that fits snugly onto my 2x28mm stainless steel axle. The paddle wheel relies on magnets to send signals to the LCD device as it rotates. I decided to design and print one myself after exhausting all other options. My fifth attempt turned out well, which I'm happy to share with you. The new paddle wheel has six paddles, two of which have recesses for tiny Neodynium magnets that I found on Amazon for under £5. These magnets are 2mm in diameter and 1mm thick but surprisingly strong considering their size. They're triple-coated to prevent oxidation, and I ended up using eight in total - two pairs per paddle wheel. Initially, I didn't realize they had to be mounted side-on, which led me to reflect on whether larger magnets would work better. In the end, I superglued them onto some flexible PLA that worked out perfectly. Use this at your own risk: I haven't fully tested it yet, but it seems to do its job and spins easily. The only caveat is that it's slightly curved at the bottom, so you'll need a little support to keep it stable.