I have a E7D MFD with radar and a P79 (thru hull) transducer. My boat is a Seahunt 234, less than one year old. MFD installed upon purchase. Shortly after we got the boat, I noticed the MFD was picking up a depth  reading intermittenly. Last few times I took the boat out, it displayed no readings. frustrating. We've had no fish finding capability. Yesterday, while I was washing the boat I noticed a reading. Is there something I should look at/for that may be causing a fault.  Thanks

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Welcome to the Raymarine Technical Forum Bernie,

Please note that fishfinders are not designed to return a bottom image or depth value when the hull is out of the water.  Begin by checking the following two items:

  • verify that the transducer reservoir is filled as the transducer is designed to transmit energy through the hull via a fluid medium (typically RV antifreeze)
  • verify that the P79 transducer has been selected within the MFD's transducer configuration settings (HOME->FISHFINDER->MENU->SET-UP->TRANSDUCER SET-UP->TRANSDUCER)
  • verify that the transducer is pinging (an automobile diagnostic stethoscope may be helpful in listing to the transducer)

Transducer location is critical to maximizing the performance of the system.  It is also important to periodically check in-hull transducer reservoir fluid levels to ensure that they are full.  Also, when operating in depths greater than 180', the 50kHz frequency is recommended.

From a performance standpoint, properly installed thru-hull transducers will typically deliver the best performance.  The performance of in-hull transducers may be as much 20% lower than a thu-hull of similar transmitting element design.  As hull designs, materials, thickness, and other factors differ, performance of in-hull transducers will vary between boats.

In order to install an in-hull transducer, the following minimum hull requirements must be met:

  • the hull must be constructed of solid, non-cored fiberglass in the location where the transducer will be installed.
  • the hull must additionally be less than 1" thick in the location where the transducer will be installed
  • the hull must not feature hull aerating steps (if so, the transducer must be located forward of the step.  Owners must recognize that such an installation location may cause the section of the hull below the transducer to loose contact with the water when the hull lifts while operating at high speed)

Before bonding the transducer reservoir to the hull's inner surface, it us recommended that this location be tested first.  In choosing the transducer mounting location, it is recommended that baseline performance of the fishfinder/transducer be established with the transducer held over the side of the vessel while the vessel is stationary and in water having a depth of at least 30'.  Suspending the transducer in this manner can also be used to test to operation of the DSM.  A series of snapshots of the fishfinder's image should be taken as a baseline to then compared the performance of proposed transducer installation location(s) while trolling, while on plane, and at high speed.  One would then rest the transducer on a ZipLock bag which has been filled with water (purge all air) and temporarily placed on the inside of the hull in the area where the transducer performance will be tested.  Transducer site testing should be performed while the vessel stationary, trolling, and when on plane until the best transducer installation location is determined.  After testing has been completed and the best installation site determined, then the transducer reservoir may be fastened to the inside of the hull per the transducer installation instructions.

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