Perhaps the following post of the Raymarine moderator gives an answer.
Displaying speed data on my MFD
Note: the command sequence specified within this response are specific to Rayamrine's a/c/e/eS/gS-Series MFDs operating with the latest software update. Should you own a different model of MFD, then please consult your product's operation instructions for the command sequences for your MFD.
Two types of speed/distance can be displayed by Raymarine's a/c/e-Series MFDs featuring internal sounder circuitry:
- GPS speed/distance of over ground (SOG), and
- speed/distance through water (Speed).
If you are be satisfied with GPS speed/distance over ground, then no additional sensors need be installed (MFD and GPS sensor) and the MFD would simply need to be configured to display COG/SOG within the Databar, within the Data application, or within the Databoxes. However, if you desire to view speed/distance through water, then a speed instrument or a compatible fishfinder transducer with speed through water transducer (may be included in the depth transducer or the depth transducer may be accessorized with a compatible speed/temp transducer) must be installed. Speed through water is particularly useful in conjunction with COG in determining through water efficiency calculations as well for trolling and sailing applications. If one currently has a depth/temp fishfinder transducer installed, onboard, speed through water may be added by additionally installing a compatible speed/temp transducer. Most sailboats or vessels operating for extended periods of time on battery would be advised to install a speed instrument as the fishfinder sonars draw more current. Installing a fishfinder sonar with a speed/temp sensor will enable a greater number of features than would be offered by installing a speed instrument alone.
If speed is provided by the fishfinder transducer, then the speed must be calibrated (HOME->FISHFINDER->MENU->SET-UP->TRANSDUCER SET-UP->SPEED OFFSET). If speed is provided by an instrument, then it must be calibrated via the instrument display. Failure to calibrate speed will cause the through water speed / log / trip and GPS speed / GPS log / GPS trip values not to match.
Please note that log/trip will generally differ from GPS log / GPS Trip due to affects of current. Under slack conditions, calibrated log / trip should be fairly close in value to GPS log / GPS Trip. Speed through water sensors feature non-linear error. As such, these sensors will be most accurate at the speed that the are calibrated at. Hi performance instruments (ST290, i70) feature multi-point speed though water calibration, while fishfinders and some instruments (ex. i40, i50, etc.) feature single-point speed through water calibration.
It is recommended that you verify that the MFD's fishfinder setting have been properly configured to specify the model of transducer installed (HOME->FISHFINDER->MENU->SET-UP->TRANSDUCER SET-UP->TRANSDUCER) (ex. B744V/B744VL, P58/P65/P66, etc), as the default transducer will be the P48, which does not feature a speed through water transducer or water temperature. When interfaced to a B744V, B744VL, P58, P65, or P66 transducer, the Speed Transducer configuration setting (HOME->FISHFINDER->MENU->SET-UP->TRANSDUCER SET-UP->SPEED TRANSDUCER) should be configured to "DEFAULT".
Like all data items supported by these MFDs, Speed may be displayed within a the Databoxes within an application page/pane as follows:
- MENU->PRESENTATION->DATABOXES SET-UP->DATABOX 2->ON
- MENU->PRESENTATION->DATABOXES SET-UP->DATABOX 2 SELECT DATA->SPEED->SPEED ... in systems lacking a speed through water transducer, select SOG instead of Speed (GPS->SOG)
