Knotmeter Calibration ... is this possible???

[barnes01]

I'm a fairly new C350 owner (Got it in December 2005) and very much a neophyte in knowing all of the systems on board and climbing through these forums like mad. I have a question on the knotmeter and didn't see any forums that addressed instruments so I'm posting this question here.

Is there a way to calibrate the knotmeter or is it's basically locked?

A couple weeks ago we were in a fairly good breeze and the knotmeter indicated we were doing 4.5 knots. I have had years of sailing experience and my feelings told me that we were going faster than 4.5 knots. I have a Garmin GPSMAP 76CS handheld GPS which I retrived to compare it's indication with the Knotmeter. The GPS indicated we were doing 6.25 Knots (Yes, I had it's units set for Knots and not MPH). This led me to believe the knotmeter may be out of calibration ... if such a thing exists. If this is not possible, what could cause the low reading of the meter? Thanks for any thoughts on the matter.

[LONGHAWK]

barnes 01, there usually is a way to calibrate. It depends on the manufacturer. Also, I know it may sound simple, but the GPS was indicating SOG. Was there any noticable current? What were the comparable readings on a reciprocal course?
Sam
LONGHAWK #173

[barnes01]

Thanks to you both. I was on Lake Lanier which has virtually no current. Delta between the GSP and knotmeter was relatively the same both directions. The instruments are Raymarine and I when I went back to the Owner's Handbook, I did find the section on calibration. Thanks. Hopefully this will allow me to correct the problem.

[Tim April IV]

Here's a link to the Raymarine ST60 Speed manual online:

http://www.raymarine.com/raymarine/Subm ... 0Speed.pdf

On page 26 (page 39 of 53 if you are following along in Acrobat ???) it has the calibration procedures.

Raymarine does a pretty good job of providing its manuals online. They should all be listed here:

http://www.raymarine.com/raymarine/Defa ... &Section=3

Good Luck!

[yodagwb]

If you figure it out let me know. I finally gave up (maybe I am a bit slow) and keep in mind its about 1.8 slow. I guess it doesn't matter because eventually it just stopped working at all with regards to speed. It will tell me SOG which it gets from the GPS and I can read with out my glasses, but speed is always 0. The paddle wheels spin freely but that's about it.
I have the directions which don't seem to matter.