Speed Paddle Wheel

ShellBack · Posted: Mon Apr 08, 2013 9:30 pm Post subject: Speed Paddle Wheel

Hi There. About half way through last season my gauge was showing zero speed over water but I did not worry about it as I was okay with the GPS and speed over ground. Now as I am soon for launching I am looking at the paddle wheel and I don't think it is touching the little sensor. Any ideas on which one wears first , paddle or sensor. Hopefully the paddle as I do not want to undo the screws for the sensor.. KO. I can change the paddle this weekend for a few bucks if I can find the right one. I hope but just asking your thoughts.
Thanks
Terry

ghone · Posted: Mon Apr 08, 2013 11:01 pm Post subject:

Hi Terry. Could be a bent axle. Does the wheel spin ok? Sometimes settings in your sounder get changed and can cause errors. You may want to check your settings so speed is On. These wheels are forever getting hit on things and quit so may have sustained damage. Most units will read while the boat is on the trailer, just turn on the sounder and spin the wheel. If it spins freely and shows 0 it's possible the wire to the wheel has a break, or ground is off or been compromised as always check all the wiring for continuity first. The wheel itself rarely fails unless broken by a hit. George

thataway · Posted: Mon Apr 08, 2013 11:10 pm Post subject:

The speed sensors rarely wear out. there are magnets in the paddle wheels and a coil in the body. With sailboats, prior to GPS the usual way (as well as a chip log or taft rail log) was a paddle wheel type. I would pull these out of the water regularly (always interesting looking at how much water comes in thru a 1.5" hole in the hull before you get the plug in the housing!. They need to be cleaned up--if the axel is bent (which rarely happened with mine) any growth or debris removed, then the axel greased with silicone grease, and light antifouling on the paddle wheels, should get you back in business.

The paddle wheel only measures speed thru the water--GPS speed over the ground.

ShellBack · Posted: Tue Apr 09, 2013 9:36 am Post subject:

Thanks Guys. The paddle is spinning freely but the gauge on the consul is reading zero. I did not know that it was done with magnets in the paddle so I understand that end now, thanks for that. I will do some wire tracing and go from there.
T

thataway · Posted: Tue Apr 09, 2013 4:20 pm Post subject:

You can apply a very low DC voltage to the gauge, and see if it works. You can also see if the coil no longer has continuity which would cause failure. If the coil (two wires going to the gauge) is open, that would be suspicious that the receiving unit is shot. Plastic could have cracked and water got into the coil.

Also spin the paddle wheel and see if there is a voltage (set on the lowest--such as 2 volts, and a good meter will read in the millivolt range. What brand is it the gauge? Is it digital or analogue? Analogue is going to be easier to trouble shoot--but less likely to fail.

ShellBack · Posted: Tue Apr 09, 2013 8:47 pm Post subject:

Hey Bob. I may have jumped the gun on asking this question without doing a bit of research. I have twin 50's Yamaha's 2009 with digital gauges to match. Home from work this afternoon with a bit of time and what I thought was a fuel pressure hose attached to the back of the gauge that was not hooked up or just a brain fart and did not think about it. Embarassed

I now think and need to trace that tube as I think that may be the way the gauge gets it reading via pressure. Not sure where the wheel feeds it's info to but it seems to be fine. [I think Confused

]

Dreamer · Posted: Wed Apr 10, 2013 12:40 pm Post subject:

Now we're talking about a whole different system. Your boat actually has 3 speed reporting systems. Speed over ground from your GPS, speed through the water from a pitot hole in the leading edge of the outboard leg and a paddle wheel which should report speed electronically to your plotter or Fish finder.

The first step would be to locate that pitot hole in the outboard leg and remove any debris that has plugged it. Of the three, my water pressure speed sensing system was the least accurate. Good luck.

thataway · Posted: Wed Apr 10, 2013 1:40 pm Post subject:

Definately as Roger says. But my experience is that the Pitot is not very accurate--especially at low speeds. It will usually be an analogue gauge.

I would be sure that the plastic tube is clear by blowing compressed air back toward the motor (not the gauge), before hooking it up.

ShellBack · Posted: Wed Apr 10, 2013 6:28 pm Post subject:

Thanks Guys. I will do some more investigating of the tube and let you know the out come.
T