Raymarine ST60 log problem

[stuey_two]

My 10 year old log intermittently shows inaccurate speed - sometimes zero when we are moving, sometimes the same speed as the GPS shows and sometimes much faster than the GPS shows - up to 20 knots, not bad for a Hunter under sail!!
I've cleaned the transducer which spins freely, and scrubbed the hull ( in case weed was hitting the impeller) without effect.
What is probable failure? Also, does anyone have experience of using Raymarine factory refurb units?

 

[hightech]

You need to feed the unit with a known pulse frequency to establish if the unit or the transducer is at fault. With the code number off the transducer tag, the airmar website will tell you how many pulses per nautical mile, you then just divide this down to a sensible speed, say 10 knots and feed that frequency of pulse to the speed input. Try a few different speeds just to check. If that works then your transducer is suspect.

 

[2383]

The log impeller has small magnets on the ends. These can de-magnetise after a while, rendering the registering of each spin of the log inaccurate. Raymarine sell replacement log impellers which are easily replaced DIY.

 

[skipperneil]

I have a ST60+ which jumps up to a ridiculous value and changes the settings such as speed units to KMH. I spoke to RayMarine at the SBS and they said that it was a known problem and to send it back to them. Haven't done so yet though.
Might be worth checking the cabling, is it being interfered with by the VHF or other device which uses a lot of current? has the cable been cut and reconnected?
Check the supply to the instrument head is clean.

Neil

 

[stuey_two]

Geoff,
Thanks for the suggestion.
Stuart