I went for a sail today and the knot meter was working and about half way thru it quit, all I had are O.O. I went down and cleaned the paddles but it still didn't work, the other functions ,water temp and trip are ok. Does anybody have any ideas. I have the Raymarine ST40. Thanks
Knot meter quit
- Thread starter Ron Roman
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Have you checked connections for corrosion? Our puck is kaput on out ST50 and we have no info at all. --.-- It will be replaced after we are hauled for the winter. I'd check connections next. SCRon Roman said:
My ST 40 knot log seems to be "off" by about 1 knot when compared to my GPS SOG. I suspect it is "junk" built up on the wheel. How do you "clean the paddles"? Dive down and scrub it off? or remove it from the inside? But what about flooding the boat?
If its a newer plastic paddle wheel housing/thru hull, just have the plug handy. On the newer ones there is a little plastic flapper that will swing closed when you pull out the paddle wheel limiting the water that enters. Still will put in a couple cups of water into the boat by the time you get the plug in, but nothing too terrible. If its the older style, well its not all that much more if your quick with you hand.
Try getting one person to roll the paddle wheel around when it's out if the socket while you are looking at the readout. If it registers speed there, but not when its back in the hole, the likely culprit is a piece of bottom growth directly in front of the transducer. I had that mystery solved after a diver cleaned the bottom and then it started working again.
I got tired of all the paddle wheel cleaning and added a seatalk gps to the system. Now at least I can get dependable speed over ground without any maintenance.
I got tired of all the paddle wheel cleaning and added a seatalk gps to the system. Now at least I can get dependable speed over ground without any maintenance.
When the speed log went dead on my 1980 Pearson 30, I had to replace the bulkhead unit where you get the read out. The paddle and the wiring were not the problem.
As an alternative to spining the wheel and trying to do it fast enough to get a reading (compressed air works well BTW) try putting it on log and spinning the wheel while you drink a beer. then go look at the log again to see if you "moved"
It is plastic, with a large plastic "nut" on the top that says "hand tighten only", but I do not see any plug around the unit. It was installed in 1996 or so by the PO, but I do not know much more than that about it. I get some speed readout, so it is not completely DOA, just reads off by around a knot when my GPS is about 3-4 knots. I tried adjusting the knot log calibration, but the "variation" is not consistent at speeds higher or lower than that.
If its from the 90s, it might not have the little flapper which means it will put in quite a bit of water per minute if not plugged. Im guessing something north of 10 GPM if you dont put your hand over it or stuff a rag in it. Could make for an exciting minute or two while you clean the paddle wheel ;-) Seeing as you dont have the plug and it doesn't sound like you have pulled it out lately, you may want to try one of the other suggestions first, or wait until you haul out next time.
I remember when I was a teenager, sailing back from hawaii and my dad swimming under the hull in the middle of the ocean to fix the paddle wheel - it didn't seem stupid at the time, but it sure does now - The only thing I can imagine is that he was too scared to pull the plug and have a hole in the hull. I pull mine in the water a couple times a year, but every time I do I have a bit of anxiety about the plug/transducer going in OK - it always does though.
I remember when I was a teenager, sailing back from hawaii and my dad swimming under the hull in the middle of the ocean to fix the paddle wheel - it didn't seem stupid at the time, but it sure does now - The only thing I can imagine is that he was too scared to pull the plug and have a hole in the hull. I pull mine in the water a couple times a year, but every time I do I have a bit of anxiety about the plug/transducer going in OK - it always does though.
Scheduled my haul out for last Saturday in October....it can wait until then!
But then again, both of my sons are PADI certified...
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