We have a tradition paddlewheel speed transducer which has become increasingly unreliable in recent years- it is 13 years old. For much of the time now it registers ‘0’.

I am looking to replacing it with an ultrasound sensor such as the one made by Airmar. Does anyone have any experience of these?
Simon

I had an Airmar ultrasonic log the whole of our circumnavigation. The advantage of ultrasound is that it doesn't need to be raised and cleaned all the time - is maintenance free. You often learn that the  paddle wheel needs cleaning when you most need to know your speed - particularly if you have been stationary for a week or so.   The disadvantage of ultrasound is that it is very sensitive - it measures the speed of the boat as it hunts on its anchor -  even a light cross current. 0.1-0.2 knots.  If you spend a week at anchor you can easily find the boat has measured a 50-100 mile passage. Switching the depth sounder instrument display off may stop the system logging the distance - or not - depending on how it is set up.

Eventually, I gave up and fitted an Airmar paddle wheel. However, 4 years on and I am thinking of returning to the ultrasound because i am fed up with cleaning the crud off!