ST60 Knotmeter

[Wayne]

I have a new (less than a year old) ST60 knotmeter that has been working like a champ until a couple of outings ago.  I keep it out of the hull when not in use--installing it when I use the boat, about every other week.  It is now beginning its day really, really slowly--hardly registering any speed at all.  Over the course of a couple of hours or so it gradually gets better and better until by the end of the day it is reporting accurately.  Is there some type of maintenance I'm unaware of?  If almost acts like the paddlewheel is sticking.  Were it above water I'd be thinking about some WD40.
Any thoughts greatly appreciated!

[Stu Jackson]

Most vendors provide replacement paddle wheel and 'wheel shaft (pins) replacements.  I know our Datamarine unit vendor does that.  Check with RM and find out if you can get a replacement, usually sold in kits.  When one of the blades of our paddle wheel got knocked off by a log we hit in SF Bay during a mid-winter storm (it was a great sail with Ken and Carol Heyman) I just ordered another one.  We keep our speedo in the tube in the water, use the boat once a week, only take it out when we rip off a blade from a great sail!

[Mike Vaccaro]

I use the same technique for pulling the paddle wheel at the end of a sortie.  We use an occasional lube of Boeing T-9 to keep it spinning freely. 

Cheers,

Mike

[Roc]

Wayne,
A fouled paddlewheel would be the first look, which is easy to see.  If it doesn't spin freely, that's the problem.  One other thing that I came across is water intrusion into the transducer itself.  If your transducer looks like it was made in two parts, the top and bottom half snapped together (see if there is a seam), then the problem might be water getting into the unit and shorting it out.  That's what happened to me.  I would have a perfectly clean paddlewheel and would be going along with nothing being registered.  After minutes or even hours, the display would start working.  Sometimes it would never work.  Turns out there was water getting into the seam.  I went through two transducers like this.  First one broke in half when I tried to remove it.  The second didn't break, but was exhibiting the same problem.  Raymarine sent me a new transducer (talked to them at the last Annapolis boat show) and this one is made in one piece.  Will try it out this summer.