Consult the Common Checks guide and make sure that all categories are fully verified.

No Water Speed

Before trying the following suggestions, turn your depth sounder on without using any options or selections to see if the problem may be in the way the depth sounder was set up to operate. Turn all features on Auto and/or set all options to "Restore Defaults" using the Setup Menu tab. If possible, check your depth sounder on a friend’s boat that has the same type of depth sounder and model number and that also has the appropriate speed gauge installed. This will indicate whether the problem is with the depth sounder or with the accessories, cables and/or installation. If the depth sounder still has the same problem on your friend’s boat, return it along with a letter explaining the problem in detail. If the depth sounder works correctly on your friend’s boat, proceed with the appropriate suggestions below:

  • Make sure your depth sounder is capable of reading boat speed. This will be shown in your Operations Manual.
  • Make sure that all necessary accessories are connected to the depth sounder. This is shown in your Operations Manual.
  • It is possible to configure some depth sounders so that no speed information is displayed even though a speed gauge is functioning properly. Check your Operations Manual and adjust your depth sounder appropriately.
  • Clear all weeds or other obstructions that may hinder the paddlewheel from spinning freely. When all obstructions had been removed, spin the paddlewheel by hand. If you get a speed-reading, then the problem is solved or the problem may be in the mounting of the paddlewheel itself. If the paddlewheel does not spin freely, then the shaft may be bent or the bushings may be worn out. If this is the case, replacement parts may be available from our Customer Service Department or you may have to replace the entire paddlewheel accessory.

Incorrect Speed Reading 

The boat speed reading on your units will vary from your boat’s speedometer or a speed derived from GPS. Typically a boat speedometer measures boat speed by water pressure on an ‘arm’ that hangs down beneath the boat, or by water pressure through a tube that runs to the speedometer. Either of these can easily become fatigued and/or clogged causing incorrect boat speed-readings.

In addition to this, if the water pressure tube is bent excessively or restricted in any way, it will cause the boat speedometer to display an incorrect speed-reading. GPS uses distance and time to calculate speed over ground. Speed over ground is not always the same as speed through water. Wind, current, and course are three major factors that can add or subtract from boat speed through water. A GPS device measures the amount of time it takes the boat to move from point ‘A’ to point ‘B’ in a straight line. Your depth sounder measures boat speed through the water by the spinning motion of the paddlewheel. This is independent of a straight-line course between points ‘A’ and ‘B’. The straightness of the course traveled is dependent on the skill of the driver of the boat. 

Installation 

  • If the paddlewheel does not have optimal installation, your speed-readings will be off. A speed gauge is like a transducer in that it needs a constant supply of turbulent free water for the most accurate high-speed readings. Every boat hull is shaped differently. It is impossible to achieve accurate speed reading on some boat hulls due to their shape.
  • The bottom of the speed gauge should be flush with the bottom of your boat. The arms that support the paddlewheel should run parallel to the hull of the boat and look like an extension of the bottom of the boat hull when viewed from the side. If they are not, it may be necessary to construct an angled wedge to mount the speed gauge on.
  • Also, be sure that the paddlewheel is oriented straightforward towards the bow of the boat. Installing the paddlewheel at an angle to the bow will not allow it to measure an accurate speed through the water. Note: Even with optimum installation, if the speed gauge is mounted behind or too close to another object on the boat’s hull, it may cause a cavitation wake that will cause the speed gauge to read incorrectly.
  • When your boat is running at high speed, the speed gauge may be lifted from the water. This will cause incorrect speed-readings, as the paddlewheel is not constantly in contact with the water.
  • Clear all weeds or other obstructions that may hinder the paddlewheel from spinning freely. If the paddlewheel does not spin freely, then the shaft may be bent or the bushings may be worn out. If this is the case, replacement parts may be available from our Customer Service Department or you may have to replace the entire speed gauge accessory.
  • Check that your depth sounder is reading in the appropriate Speed Units: MPH for Miles Per Hour, KTS for Knots, KPH for Kilometers Per Hour. If the depth sounder is reading in the wrong speed units, select the proper speed units as shown in your Operations Manual. If you cannot select the speed units, send your depth sounder in to the Repair Center along with a letter explaining the speed units you would like the depth sounder to read in. NOTE: Not all depth sounders are capable of reading in MPH, KTS or KPH. Check you Operations Manual to make sure that your depth sounder has this capability.

 f you are still having problems after trying the preceding suggestions, return your depth sounder along with the power cable, transducer(s) and any accessories (switches, temp, speed, etc.) and a letter with a detailed description of your problems to: 

Johnson Outdoors Marine Electronics
Attn: Service Department
678 Humminbird Lane
Eufaula, AL 36027

1-800-633-1468
Email:  service@humminbird.com