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Full Version: [DG11] i40 Depth with P79 Transducer erratic readings
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I am using i40 Depth connected to a P79 In-hull transducer on a Shrimper 17 daysailer. Correct cables used.

At times depth shown appears to be valid and changes as expected. On occasion though the reading with show 1ft, even when clearly there is more depth. The unit after some time will then revert to what appears to be a normal reading. Unable to identify yet what circumstances trigger the behaviour. Raising or lowering the centre plate is not a factor as the plate is normally down. It may be triggered by entering shallower water.

Any ideas what I should do to investigate/correct?
Hi Saah,

Thankyou for your enquiry.

The issue maybe the i40 and so I suspect this may need to be changed out through a local agent or direct with ourselves.

Please PM me with your details and I will contact you direct


I have exactly the same issue. When not moving in the water i read 1ft (0.3m), when i'm moving the reading is correct. When i stop moving, i read after 2-5 minuts again 0,3m.
Do you have information about this problem.

Hi BoBat,
Thank you for your enquiry

This sounds like an issue with interference, either electrical, possibly spare coiled cable affecting the sensitivity of the transducer and causing 'pick-up' hence the 0.3m reading, or could there be some physical issue on the outside of the hull, water flow from an inlet/ outlet, interaction with antifouling or even a sonic anti foul system perhaps?

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