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Loss of reported depth and ability to produce a bottom plot
01-07-16, 06:53 PM (This post was last modified: 06-14-17 09:49 AM by Chuck - Raymarine - Moderator.)
Post: #1
Loss of reported depth and ability to produce a bottom plot
Loss of reported depth and ability to produce a bottom plot

Loss of reported depth and ability to produce a bottom plot will occur if the incorrect model of transducers have been selected within the Fishfinder Settings, the depth transducer is exposed to a aerated flow of water across its face, or if the connection between the fishfinder's transducer socket and transducer cable is intermittent. Start by ensuring that the transducer plug and socket are free of corrosion, that the transducer plug is firmly seated in the transducer socket, and the transducer plug's locking ring is present and has been rotated into the lock position. This problem can also be caused by incorrect transducer selection (ex. installing a transom mounted transducer on a vessel having trim tabs, installing a transom mounted transducer on an inboard powered vessel, etc.) and/or incorrect transducer installation (ex. mounting a transom mounted transducer too high, too low, or at the incorrect angle, mounting the transducer on the port side of the transom, etc.), and/or marine growth on the hull or transducer. Please refer to the transducer installation instructions to ensure that the transducer is properly installed. In many cases, the problem may be solved by lowering the aft end of the transducer a notch or two. All hulls are not universally suited to transom mounted transducers and such determinations can only be made through trial and error. Many customers will install a transducer mounting block on the transom to permit multiple transducer mounting locations to be tested, while limiting the number of holes in the transom to those required to secure the transducer mounting block to the transom. Should the desired performance not be achieved using a transom mounted transducer, then one should consider installation of a thru-hull or in-hull transducer.

When installing an in-hull or thru-hull transducer:
- if installing an in-hull transducer, the hull must be less than 1" thick in the location where the transducer will be installed
- if installing an in-hull transducer, the hull cannot be constructed using coring materials (ex. balsa, foam, etc.)
- one should perform water bag testing to determine the best location (if any is possible) for installing the transducer. To do so, a zip lock bag should be filled with water and all air should be removed from the bag. The bag should then be placed in contact with the hull in the location to be tested. The transducer should then be secured on the upper surface to the bag. The transducer's energy will be transmitted through the water bag, through the hull, and into the body of water. The vessel should be operated at stationary, trolling, and planing speeds to test performance for the intended transducer location.
- if an in-hull transducer has been properly installed onboard the vessel and you are experiencing no reported depth and/or plot, inspect the transducer's reservoir to ensure that it is full of the recommended fluid.

Freezing or stoppage of scrolling (coupled with depth flashing) may also occur due software errors ... be certain that your products have been updated with the latest available software.

Incorrect configuration of the speed transducer speed transducer setting within the Fishfinder Transducer Setting dialog of systems using 50/200kHz fishfinder transducers is critical and vessels not equipped with a speed transducer must be certain to select NONE from the list of speed transducer configuration settings. Marine growth on the transducer and hull may cause loss of bottom and as such (particularly planing speeds and speeds approaching plane), the hull should be inspected to ensure that the transducer and hull are free of such growth. Hull protrusions (ex. steps) and other thru-hull forward of the transducers can also cause transducer aeration at planing speeds and speeds approaching plane causing the fishfinder to loose contact with the bottom. In the case of the latter, relocating the transducer or using a different type of transducer may be the only way to correct the problem. Transducer aeration can be fault isolated by testing the equipment while the vessel is stationary or at trolling speeds. Should the problem not be reproducible while the vessel is stationary or operating at trolling speeds, then it would appear that there is an aeration issue and consideration should be given to relocating the transducer. Should you feel that the correct transducer has been installed and that it has been installed properly, then please attach some pictures of the transducer (from side and rear, transom, and hull bottom and attach them to this incident for further analysis.

[Image: attachment.php?aid=70]

Should transducer aeration not be taking place and bottom loss occur when using the auto gain and range settings, then it may be necessary to manually configure the Gain and/or Range settings. When operating in depths greater than 250', it is recommended that the fishfinder be configured for 50kHz or dual frequency. Generally, performance may be further enhanced by manually increasing the Gain and Color Gain configuration settings. Finally, should the Gain adjustment not address the problem, then manually configuring the Range setting and adjusting the range to be slightly greater than the spot soundings of depth contours on the chart for the vessel's location.

For shallow water operation, the 200kHz frequency would typically be used, but you may also want to try 50kHz ... this recommendation is not applicable to CHIRP/DownVision transducers. It may be necessary to reduce the power setting to as low as 20% in very shallow water to avoid multiple reflections and maintain contact with the bottom in systems not featuring CHIRP/DownVision transducers. One should not normally expect depth readings in depths less than 3' below the transducer from a fishfinder. Fishfinders should not normally be tested while the vessel is out of the water as the fishfinder will not be able to report a depth value (i.e. sound propagates differently through air than water). One may however test the that the transducer is pinging by listening for audible ticks or sensing the transducer pings with one's fingertips placed on the bottom of the transducer when the fishfinder is on. Should the transducer be pinging, then it is recommended that the fishfinder be sent to Raymarine’s Product Repair Center to be bench checked / serviced.

Should one feel that the correct transducer for the application has been installed and that it has been installed properly, then it would be recommended that several photos of the transducer (from side and rear), transom, and hull bottom be attached to any threads/posts seeking support for bottom loss.

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