Nasa Clipper Duet problem

[dgadee]

I put a Nasa Duet on the boat a few years ago. The depth reading works but the speed hasn't worked for years. I never really bothered with it since SOG was more interesting. However, re-sorting the electrics I thought it might be worth getting it to work. The wheel turns easily, is set in the correct direction and the wiring seems to be in v good condition. It just displays 0 knots. Any suggestions as to how to test this? If it's a dud sender I would replace that. If not, I'll just keep the device and accept operating only for depth.

It is this one:

 

[Minerva]

I'd check that the paddle wheel still has a wee magnet in one of the vanes and it hasn't fallen out. A replacement part is very cheap. Also Nasa are very responsive to emails / calls and their customer service in my experience is exemplary.

just make sure you don't inadvertently phone the American ones - they might not be so helpful!

 

[SteveG]

Minerva could be right about the magnet, I have had that too.
Had similar issue following anti-fouling my hull one year. The antifouling had crept up inside the paddle wheel mounting tube and was fouling in the impeller.
If the magnet is there, try spinning the impeller after withdrawing it from the mounting tube - don't forget the cap to stop water ingress!! At least you will know it is definitely rotating then.
I have connectors on my transducers and keep a spare, so I can swap them if I get weed on the impeller and therefore only get one lot of water sloshing about each time.
Best of luck, S

 

[Rum Run]

The NASA impeller has two magnets I think. One vanished on mine and it accurately measured half speed.
New impellers are about a tenner so not bad for a boat part

 

[dgadee]

Thanks, all. Paddles are very cheap so will replace and get a spare, too.

 

[LittleSister]

I had a minor issue with a NASA Duet paddle wheel. The paddlewheel appeared to turn fine when retracted, and usually worked but sometimes didn't. I eventually deduced that it was somehow catching the housing slightly, preventing rotation, depending on exactly what position it was in.

Lining it up with the indicating fore/aft arrow (or line or whatever it was, I forget now) wasn't necessarily enough. If, once under way, it wasn't reading it was simply solved by rotating, ever so slightly - only a couple of degrees, I guess - the paddlewheel one way or the other in the housing and off it would go, and be fine (bar any fouling) until the next time it was withdrawn. (I think I recall that when it worked it looked like it wasn't exactly in line with the arrow/line, but just a fraction to one side.)

Despite closely inspecting both the paddlewheel and, when the boat was out of the water, the outer end of the housing, I couldn't see what was fouling what, but as the solution, once discovered, was so easy, I never bothered to explore further.