anyone tried to change a paddlewheel on speed log?

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Mike k

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I have a navman through hull fitting with paddlewheel. Well the paddlewheel is missing ,must have been knocked off on a lift out. I have bought a replacement full unit but I don't fancy rewiring everything and wondered if I could remove the paddle wheel from new unit and fit to old. It looks like the core pulls out but wouldn't fancy doing this in the water even though they supply a plug. I am coming out of water tomorrow so if its straight forward might give it a go.Thanks for any tips/advice
 
Mike k said:
wondered if I could remove the paddle wheel from new unit and fit to old.
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It is definitely feasible with some Raymarine speed transducers, and the paddlewheel is in fact available as a spare, as per this example.
Not sure about Navman, but it might well be that they are actually using the very same stuff - more than likely built by Airmar.
And yes, the plug is meant for pulling out the core unit also with the boat in the water.
I understand your concern, but if you don't mind just a bit of water ingress, it does work.
 
I have done this on a Plastimo 1985 vintage log.

The impeller pin could be pushed out through its housing.

The impeller was a standard spare part, along with its pin.

If your replacement is second hand, check it first. Some have a little magnet in them, if it's gone, it won't work.
 
Just junked the Navman transducer yesterday (ashore). I had lost the paddlewheel. The transducer has a simple pin the release and then the transducer could be pulled using an unscrewing twist. It isn't actually 'unscrewing' the transducer but it is recommended to use an unscrewing twist to release. Wasn't easy to withdraw. The plug suitably silicon gel'ed went into place ok.

My location wasn't the greatest to withdraw if she had still be afloat but with good access it would only be one armful of water.
 
The transducer is meant to be withdrawn and replaced with the plug when the boat is to be lifted in slings, to prevent damage to the paddlewheel. It's also a good idea to do this when the boat is afloat but not going to be used for some time, particularly in high fouling areas. The plug should have the same mechanism as the transducer, for locking in place, and seals to prevent water ingress.
If done deftly, removal and replacement with the plug can be done in 2 or 3 seconds, and only a small quantity of water will need to be sponged out of the bilge.
 
PetiteFleur said:
I've also done this on a NASA log several years ago but I was ashore.
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Ditto on my NASA log. It was easy enough to change and the iron core had rusted through the plastic on the log wheel proving that plastic does absorb water.

If doing the change afloat I suppose the only precaution I can suggest is that if the screw cap either cross threads or does not prove water tight, that you have a rubber universal bung handy like I have in my plumbing kit. I guarantee you will never need it, apart from the day you don't have it handy.
 
Havent
Alfie168 said:
Ditto on my NASA log. It was easy enough to change and the iron core had rusted through the plastic on the log wheel proving that plastic does absorb water.

If doing the change afloat I suppose the only precaution I can suggest is that if the screw cap either cross threads or does not prove water tight, that you have a rubber universal bung handy like I have in my plumbing kit. I guarantee you will never need it, apart from the day you don't have it handy.
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seen you for a while! how are we?
 
I have changed the paddle wheel on my Navman log. Simply bend apart the legs that hold the pin and click the new wheel with pin back in. 30 second job. Withdrawing the log let’s a little water in, do you have the screw on blank plug To quickly screw on?
 
There's also the option of doing away with the paddlewheel unit completely and replacing it with a GPS-enabled device which simulates and sends the pulses to your plotter: It can be used in f.i. Raymarine ST40 or ST60 type units from which real wind direction can be calculated.
The only catch is that it sends SOG data and not Speed Over Water so it doesn't consider currents.

CruzPro SOG2 GPS NMEA 0183 to Paddlewheel Speed Pulse Converter.
or


https://www.aragon-technologies.com/fr/electronique-marine/remplacement_des_capteurs_de_vitesse_a_roue_a_aubes.php
 
I've done this loads of times. On a NASA instrument they supply a blanking cap so you can cap it off and change the impeller at your leisure. Make sure you have anything you need easily to hand. When replacing the sensor, unscrew the cap but keep a little pressure on it you can then lift the cap and insert the sensor in a matter of seconds.
 
I would add that you have to
be very careful with plastic fittings as these are easy to cross thread. Don't know if this is relevant to your particular model.
 
Mike k said:
I have a navman through hull fitting with paddlewheel. Well the paddlewheel is missing ,must have been knocked off on a lift out. I have bought a replacement full unit but I don't fancy rewiring everything and wondered if I could remove the paddle wheel from new unit and fit to old. It looks like the core pulls out but wouldn't fancy doing this in the water even though they supply a plug. I am coming out of water tomorrow so if its straight forward might give it a go.Thanks for any tips/advice
Click to expand...
You could replace it with a NASA Electromagnetic transducer. No more paddlewheel to clean or replace.
 
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