Paddlewheel Speedo on Pontoon

rickdb1boat · #1 June 24th, 2002, 01:03 PM

Hi All, I just aquired a different pontoon boat and have a Humminbird Fish Finder w/ Speed & Temp probes. The speedo uses a paddlewheel type pick-up. On my old toon, I mounted the transducer on the bracket on the starboard side and just screwed the paddlewheel into the port toon a little left off center to avoid getting a false reading from the flow of water of the bottom of the log. This time I went ahead and mounted both of them on the same bracket on the right side and the speed and distance reading are way off! I think the tranducer is messing with the flow to the paddlewheel! Any suggestions as how to mount the paddlewheel or where? The way I had it on my old boat worked fine, right on the money for speed and distance! I'm sure having it right next to the transducer, not to mention directly under the log where I'm getting turbulant water flow, is the culprit! Any help would be appreciated! Thanks, Rick

FlyBoyMark · #2 June 24th, 2002, 08:32 PM

Paddle wheel should be mounted on exactly the bottom of the bracket by itself. You will get erronious readings because of accelerated flow of water around the float(pontoon) because the water has to move out of the way to allow the pontoon to move forward. Any other devices in the proximity will aggravate this phenomenom because it will accelerate the water further for it to move around the object it is displacing. (hydrodynamics 101 ) There is still an error on the bottom but usually only about 1 to 3 MPH.

rickdb1boat · #3 June 25th, 2002, 05:36 AM

FlyBoyMark,

Thanks for the info! I just did'nt know if the pick-up had to be mounted to the side of the log to avoid the turbulance that occurs from the log. I can only guess that by mounting it right next to the transducer, is throwing my reading off so far(About 7 MPH). I really am not so concerned about the speed part, as I am the distance reading being accurate, which of course, also depends on the speedo be close to correct! I guess my best bet would be to have another bracket welded onto the left toon and mount the pick-up there! Thanks, Rick

FlyBoyMark · #4 June 25th, 2002, 08:26 AM

Some models of sonar have a correction item in the menue to calibrate this speed difference. My Eagle Accura 240 does....