798 Transom Mount Transducer Flipping Up

Humminbird Fish Finders, Transducers, mounts, etc...
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Posts: 4
Joined: Mon Apr 16, 2012 6:45 pm

798 Transom Mount Transducer Flipping Up

Post by rod2605 » Tue May 15, 2012 8:55 pm

Hi Greg,

We have a 798ci HD Si with a standard transom mount transducer on a 5.8m Fibregalss boat which we use for fishing in open waters.

We have had no end of trouble with the transducer flipping up at any speeds above 35mph. We have tried replacing the bracket, adding some adhesive between the braket and the transducer to assist to hold it in place and in desparation even tried adding the screw to lock the transducer in the down position but this only resulted in the bracket breaking. Top speed of the vessel is approx 66 kph (42mph).

The installation of the transducer is as per the instructions - it is installed on the RHS of the transom (looking from the back) with the centre line (height wise) of the left hand edge of the transducer lining up with the bottom edge of the transom. The angle of the transom is approx 30deg so this means the centre line of the right hand edge of the transducer is approximately 40-50 mm (1.5 - 2 inches) below the bottom edge of the transom.

Does our installation sound correct?
Would you expect the transducer to flip up at 40mph?
Can you provide any suggestions as to a rememdy? I could obviously lift it up but I am concerned that this will increase turbulence and therefore performance at speed.


Posts: 4482
Joined: Tue Apr 17, 2007 6:26 pm
Location: Eufaula, AL.

Post by Humminbird_Greg » Fri May 18, 2012 12:24 pm

The installation instructions are written in a more general sense and not specific to each boat. It sounds like you would need to raise the transducer upwards to keep it from kicking up. Doing so may not allow it to operate at higher boat speeds though. Often it is not the constant speed of the boat that causes this problem; rather it is the pounding the transducer takes from coming off a one wave into the next.
Greg Walters at Humminbird
I help because I can

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