Thanks for your input Dockhead !
Too bad it turns out that it isn't the magic bullet I was hoping for. For the cost of that transducer I would expect perfect operation.
You haul every 2 - 4 months ???? Wow !!! Around here a haulout and pressure washing
sets you back close to $600 (for a 36 ft boat) each time.
I have a bit more information for those that are following this thread.
About a month and a bit ago I decided that my (boat) bottom needed a good cleaning. As it turned out, a quick going over with a sponge did no good and I had to attack things with more vigor. I used a scrub brush over three dives to remove all crud but also noticed that the scrub brush didn't seem to do the ablative bottom paint
(which was already very tired and I was hoping for it to hold up until winter) any good. I was suitably impressed with the speed the boat had picked up! Fast forward 4 weeks and you could pretty much see 'stuff' growing on a daily basis. The hull
looked worse than before scrubbing and speed was way down again. Add to that the inexplicable poor paddlewheel performance and I was all set to replace the speed sensor on the upcoming haul.
I had one last trip planned before the haul and the paddlewheel had stopped for good again. I decided to pull it and clean it up for the trip. Holy cow, that poor sensor was ALIVE with critters. You could literally see movement everywhere you looked and after a lot of brushing and cleaning I ended up with maybe 20 or more 'things' that moved on the sole. I had NEVER encountered anything like this before - a bit of slime sure but not a heaving mass of critters.
So here is my interpretation of all this .... and there is some guesswork involved ....
I now believe that whatever little bit of anti fouling
properties were sill present in my old bottom coat ended up coming off when I scrubbed the bottom. With no protection left at all, the boat bottom became alive with all manner of 'stuff'. Said 'stuff' also took up residency in the paddlewheel. I believe the cloud of antifoul (as it leached out in normal operation) that previously floated by the paddlewheel kept growth in check even though the wheel itself had not been coated.
This morning, in prep for the haul out
tomorrow, I pulled the paddle wheel sensor again and although not quite as bad as before, it might have been jammed already from marine
I interpret all of this, and my previous reasonable paddle wheel operation when the bottom had a good coat of antifoul, as a clear sign that my issue was the dead antifoul (I am not sure but it might be the third year for the bottom).
I will be painting the sensor with a coat of antifoul when the bottom gets done as well and hope that performance, although far from perfect, will return to acceptable.
If operation still ends up as marginal, I will replace the paddlewheel next.