Hummingbird Interference at moderate speed?????

I have a Hummingbird fish finder with a through hull transducer mounted under the motor on a 17.5' 1976 Campion. At slow trolling speeds it seems to work just fine but at moderate speeds or especially when slowing down it the screen is littered with fish symbols. At cruising speed it seems to read the depth correctly.

I believe that it must have something to do with the location of the transducer and/or the hyrdaulics under the boat at these speeds. Could it be that whoever installed the transducer didn't quite have it seated down all the way and there is an air gap between the puck and the bottom of the boat? How do I remove the transducer without damaging it and what do I use to reattach it? Where is the best location to prevent my interference problems? The transducer is right beside the bilge pump and pretty much right over the keel 18" from the stern.

I have played around with the settings but haven't been able to solve this problem.

Any ideas, thoughts or suggestions?

Re: Hummingbird Interference at moderate speed?????

It cannot be located over anything that creates air bubbles such as the keel or strakes. If it is directly over the keel it needs to be moved.

Re: Hummingbird Interference at moderate speed?????

Any tricks to remove? Do I just move it 10" to either side? What do I use to reattach it? Is there a way that I can temporarily attach it to different spots to test it's effectiveness? And last question, do I sand the spot clean before attaching to ensure a proper bond?

Re: Hummingbird Interference at moderate speed?????

I have no idea what it is held down with so I can offer no advice on how to remove it. The surface of the transducer must be set with an adhesive that will not have ANY air bubbles init when cured. Some folks bond a small container to the hull then fill it with mineral oil. Teh transducer sits in the mineral oil. A good amount of epoxy can also work. You need to look at the bottom of the boat and find a clear spot as close to the transom as possible. No rivet lines, no strakes, must be under the puck. Transducers cannot read through air.

Re: Hummingbird Interference at moderate speed?????

Thanks, I got the old one off. I'll have to clean it off and use some sort of epoxy and try a location closer to the transom away from the keel. I'd imagine a light sanding will help with the bond.

Re: Hummingbird Interference at moderate speed?????

Sanding always helps w/the bond. Location away from turbulance is key. Also direction of signal upon final setting is important.

Re: Hummingbird Interference at moderate speed?????

And suggestions on what epoxy to use to adhere the transducer

Re: Hummingbird Interference at moderate speed?????

Rarely is silicone advised on a boat, but that is what i would use. Just be sure to avoid "ANY" air pockets or bubbles.