We just got our boat in the water and the knot meter dosen't seem to be working. It spins freely and isn't clogged. We checked it underneath before we launched her and then took it out and put it back in once we were in the water as well. It registers on the read-out when you spin it with your hand but when in place, it reads very slow or negative numbers. Any ideas?
Tom Plummer
Member III
Could it be 180 Deg. out of position? If it is then it is turning backwards hence negitive numbers.
Is the transducer in all the way? If it is only partially down through the mounting tube then there wil be a little vortex in the indent in the hull so who knows what the reading would be. Did it work installed like this in the past? Assuming the water isn't too cold, probbaly the best way to check that the paddle wheel is extending below the hull into water flow would be to swim dowm and see for yourself...
Geoff Johnson
Fellow Ericson Owner
The logic is appealing but are knotmeters really smart enough to know which way the paddle wheel is spinning? I would have thought they just count the number of times a magnetic sensor passes a certain point over time.
Tom Plummer
Member III
I too would have thought it would be a simple magnetic pickop but them how do you get negitive numbers?
Geoff Johnson
Fellow Ericson Owner
Don't know, but it has great possibilities for kids who want to take their parents boat out for an unauthorized sail . . . they just have to sail backwards half the time (like Ferris Beuhler's Day Off, but then that didn't turn out so well).
ted_reshetiloff
Contributing Partner
My Datamarine meter worked great all last year. This year I put a new max prop on and thought I had the pitch right but at 2200 rpms I was 1.5kts slower than expected. Meter showed only 5.5-5.8. Turned on the gps and ran both ways to cancel current effects and got 6.8-7.2kts. More like what I expected. Went for a weekend cruise and the damn thing read 1.5 kts slow all weekend. I know its clean, so I ask whiskey tango foxtrot? Maybe the transducer is old and the contacts in it are building up too much resistance... I have about $300 into patching up my datamarine wind, depth and speed meters. They all have been performing great until this point. I really dont want to put any more $$ into these old things but I aint exactly ready to drop the coin for a new set and to have to deal with the square meter in a round hole issue either. Hopefully it turns out to be something easy to fix, I really havent checked. Been to busy enjoying the shher pleasure of how well my boat sails this year with a racing bottom and new running rigging, but thats another post.
calibration
I had a strange phenomenon last year when my knotmeter all of a sudden read low as well. No changes otherwise. During the winter I looked through the manuals and found that the meter can be calibrated. Haven't looked at the process yet but it seems that there is a timer or something that needs to be set and reset. I have the original Datamarine setup on a 1988.
As soon as I launch next week (...) I'll get on it.
Chris
I had a strange phenomenon last year when my knotmeter all of a sudden read low as well. No changes otherwise. During the winter I looked through the manuals and found that the meter can be calibrated. Haven't looked at the process yet but it seems that there is a timer or something that needs to be set and reset. I have the original Datamarine setup on a 1988.
As soon as I launch next week (...) I'll get on it.
Chris
Shadowfax
Member III
FWIW
On my 34 there is a access port that you open to get to both transducers. This is also a very nice spot to put the electric heater. I noticed once that with the heater on in this location that my knot meter was reading about 40 knots and slowed with fan speed. Could this be simple polarity problem?
On my 34 there is a access port that you open to get to both transducers. This is also a very nice spot to put the electric heater. I noticed once that with the heater on in this location that my knot meter was reading about 40 knots and slowed with fan speed. Could this be simple polarity problem?
What kind of knotmeter ?
Omgirl, is that a Datamarine knotmeter ? I've had Datamarine and Raymarine but I don't recall them actually reading negative.
Stupid question: Is it possible that the paddlewheel is somehow being inserted 90 degrees to the waterflow instead of with the waterflow ?
-- neal
Omgirl, is that a Datamarine knotmeter ? I've had Datamarine and Raymarine but I don't recall them actually reading negative.
Stupid question: Is it possible that the paddlewheel is somehow being inserted 90 degrees to the waterflow instead of with the waterflow ?
-- neal
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Geoff Johnson
Fellow Ericson Owner
I am not sure it is possible to reverse polarity as the transducer is connected by coax cable on Datamarine units.
I once had a problem with ratty data from a Datamarine depth sounder that was caused by moisture intrusion/corrosion in the cable. Someone put a pair of bnc connectors right before the transducer and the humidty above the bilge was enough to degrade it near the connectors.
Anyway since Omgirl's speedlog seems to work when they spin it by hand it doesn't sound like a cable problem.
I suppose this still could be a cable problem.
Omgirl, have you tried to manipulate the cable while spinning the paddle wheel on the transducer ?
-- neal
Anyway since Omgirl's speedlog seems to work when they spin it by hand it doesn't sound like a cable problem.
I suppose this still could be a cable problem.
Omgirl, have you tried to manipulate the cable while spinning the paddle wheel on the transducer ?
-- neal