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Knowledge Base

How can I make sure the impeller sensor (coil) is mounted directly above the impeller?

Below is a procedure that has been successful for other customers:


  • Two People
  • One Sharpie
  • Goof-Off
  • wiping cloth or paper towel


  1. Put the boat in slings right side up.
  2. Assuming the speed pickup is installed so that it is aligned parallel to the long axis of the hull, put one forefinger on the tip of the pickup furthest from the cable that connects it to the cradle. Then try to put the other forefinger on the bottom of the hull in the location where it would touch the other forefinger if the hull were not there. Use the Sharpie to make a dot marking that spot.
  3. Hold the impeller unit against the hull so the impeller propeller is next to that dot.
  4. Put the SpeedCoach into the cradle, turn it on, and set it to read speed via impeller.
  5. Make the impeller spin by blowing on it and see have your helper see if a speed reading appears on the SpeedCoach. If not, try moving the impeller unit forwards and then backwards and blow on it to find where you get a reading.
  6. Once you have a reading, mark that spot if it is different from the spot where your forefinger was.
  7. Then define the range where you can get a reading, by moving the impeller unit forwards, finding the spot where readings cease, and marking that spot. Then move it backwards and mark the spot where readings cease.
  8. Center the impeller unit between those two locations, mark that spot, and attach the unit to the hull with VHB tape
  9. Test again by blowing on it to confirm that it works.
  10. Use Goof Off to wipe away the markings

This method will work for ANY SpeedCoach impeller mounting.