Speed over ground VS Paddle wheel?

[MarkNY]

i recently installed another sonar unit on my boat that has a paddle wheel for surface speed. Today while out on the boat i noticed that the paddle wheel is about 1 mph slower than SOG on my other unit at trolling speed but when i get up on plane the paddle wheel jumps in front of SOG and is way off. example SOG 25 and paddle wheel 38. not sure if i installed the paddle wheel correctly. i lined up the mount with the deadrise of the boat as opposed to mounting it horizontally like a transducer. any thoughts on this issue? thanks, mark

[jigstick]

This is pretty typical.  My VHF has a built in GPS on it.  My Chartplotter also has GPS.  My Sonar box and transducer has a paddle wheel.  For SOG, my VHF and Chartplotter are identical.  They are pulling speed from the satellites, which does not take into consideration any water currents /  waves.  My paddle wheel reading is always different than the other two, because it DOES take into consideration the currents.  For trolling purposes, I would use the reading from the paddle wheel.  Because that is how fast you are going IN RELATION to the surface of the water.  Your STW is always going to be different than your SOG.

[LongLine]

Paddlewheel readings can be very misleading due to the nature of where they are located and the size of your boat.  i.e. how deep you're sitting in the water.  Next time your trolling, take a look at the water at your transom. Look at the currents that swirl around.  Even with paddlewheel rigg'r probes, they recommend lowering them at least a couple ft below boat to check speed calibration. 

 

Also remember that the important thing is repeatability, not the exact real speed that you're going. 

 

Tom B.

(LongLine)

[jimski2]

Compare your lures action with the paddle wheel speed and determine the most effective fishing speed for your paddle wheel indicator. Speed over ground is not what your water speed is due to currents that effect your lures action. You must consider that in the lake there are currents the same as in a river. Air pressure systems and winds change the level of the lake from one end to the other all the time so a lot of water moves back and forth or even stops moving at times. You become aware of certain steering courses are better at catching fish some days and the currents have a lot to do with that. A change of a three quarter knot in the direction will make your lures ineffective.

[MarkNY]

Thanks guys. I know alot of times when salmon fishing i control speed by watching the gear so next time i fish ill have to see how the paddle wheel speed comes into play when i have a full spread out. best, mark

[rolmops]

Thanks guys. I know alot of times when salmon fishing i control speed by watching the gear so next time i fish ill have to see how the paddle wheel speed comes into play when i have a full spread out. best, mark

You can easily do it in Owasco lake. With a northern wind the currents in the lake move to the south and with a southern wind,the currents move to the north