Autohelm ST30 Speed error

[Capt Guido]

Recently my ST30 speed display is off by nearly 1.5kn on the low side compared to my GPS reading. I've taken out the transducer and cleaned the wheel, made sure I inserted correctly with the flat side facing the bow, and maxed out on the calibration at 1.50. When running my Hunter 29.5 @ 2900rpm the GPS reads 6.4kn compared to the ST30 @ 4.8kn.

The only thing I can think of is to replace the paddle wheel. Tried to locate a source with no luck.

Open to any and all suggestions.

 

[jimq26]

Doubt you will get them to match.

Speed over ground (GPS), and speed through the water (ST30) are two different things altogether.

 

[Dennis W.]

SpeedCheck

Minnie, After you do the speed check on one course then do the reciprocal. Several checks on several varied courses with reciprocals will establish the actual error. You may have to replace the whole unit, less than $100.00 and no need to haul the boat.