Fishfinder sender install question

Installing a Hummingbird Pirhana 20 portable unit in Old Town Predator.

Is it possible with this type kayak to install the sensor inside the hull rather than the temp/suction cup mount on the side? I read some posts that were pro/con on performance thru the hull (on some kayaks) due to the multi-layer construction and material.

Any experience with Hummingbird units performance?

Ideal location would be in the bow, out of the way.


Pirhana Test

Put a 1/4 inch or so of water in the bottom of your boat, put the transponder in the water (should be directly infront of you so you can watch and move it as necessary), then go for a paddle. The Pirhana is a very good unit with plenty of adjustable sensitivity to do the job through a homogeneous material such as composit and plastic constructions - unless they are quite thick or there are voids with air in them.

If the Hummingbird works through the water, then you can epoxy it in the location of your choice - as long as there is no air between the bottom of the transducer and the hull, and the hull and the water. Also, the thinner the epoxy layre between the transponder and the hull (flat surface to flat surface is best), the better sensitivity you will enjoy.

That said, I use the suction cup as close to the stern as possible with very few problems. - JJ

got a scupper pro that I put a pirahna on. Used clear silicone to attach the puck in shoot through the hull fashion. Have had problems getting it to adhere for very long, despite roughing up the plastic with sandpaper before attaching. Going to try some other adhesives this spring. Check the archives of for more commentary on the subject.


I have a Piranha portable. I shoot through the hull. Just put a large glob of vasiline onto the transducer and stick it to the floor. Hold it down with duct tape. That’s what I do and it works quite well.