Section 27 - Fishfinder

I'll admit that this may not be an item everyone would want on their kayak. I chose to install one because it enables me to find new dive sites. It gives me a constant readout of my depth, bottom contour, and fish when present. I am using the Humminbird 100SX fishfinder. It is around $100, is waterproof, and uses a single beam transducer. This was important because multiple beam transducers require the transducer to be facing forward to operate properly. The single beam does not. This fishfinder is operated by a 12 volt rechargeable sealed gel cell battery in a watertight case and placed in the front hatch. I purchased the battery at a hobby shop for around $40. I purchased the neoprene cover and the "Micro R-A-M Mounting System" from Cabela's online for around $50. Be sure to order the base that specifically fits your brand of fish finder. It is all removable except for the ball mounted on the kayak.

The Humminbird 100SX Fishfinder

Neoprene cover for the screen portion of the unit

The Power Plug

The power cord can be cut to the desired length. Because the wires plug into the bottom of this unit it is more convenient to leave them permanently attached with the use of the R.A.M. mounting system. Regardless of the fishfinder brand you must install an inline plug on the power supply cord in order to be able to disconnect it from the battery in the kayak front hatch. I used a two lead trailer wire plug from an auto parts store and some heat shrink (blue in the photo) to seal the connections. The rubber plug is to insert into a hole drilled in the kayak. 

The Transducer

The transducer cord CANNOT BE CUT so curl up the excess and secure it with cable ties. I have attached it to a block of high density foam material with cable ties so it does not make hard contact with the bottom of the kayak. I also attached cable ties to the bungee cord itself on each side of the transducer to keep it in the center of the cord. It is critical that the transducer be centered on the bottom of the kayak in order to obtain accurate depth readings. If it is at an angle under the kayak it will give you deeper readings because the beam is transmitting at an angle. DON'T FORGET to unhook the transducer before landing the kayak on shore.


I also use a piece of high density foam to protect the transducer when not in use. The bungee cord wraps around the foam pieces to keep them together.

The Micro R-A-M Mounting System

The Micro R-A-M Mounting System consists of 3 sections: 

1. Top ball/platform for attaching the base of the fish finder to (use stainless steel nuts & bolts.)
2. Center section which allows the unit to pivot into many positions on the rubber like balls.
3. Bottom ball/base which is permanently attached to the kayak (use stainless steel nuts & bolts and a 1/4" plexiglass circle on the interior of the kayak for reinforcement.)

A hole is drilled in the kayak (shown with a plug in it) to accommodate the battery wire from the fish finder to the battery pack which goes in the front hatch. The extra plug tethered to the ball on the kayak covers the hole when paddling without the fish finder on board. The plugs are drain plugs from an earlier model of the Scrambler XT and can be purchased at an Ocean Kayak dealer. You can use any pliable rubber type plug.

The Battery

The battery is in a watertight case made by Underwater Kinetics. It fit the battery size by pure coincidence. I drilled a hole in the case for the power cord and cut the cord to the desired length.  Both sides of the hole in the case are sealed with Marine Goop. The battery should be stored upright when not in use. High density foam blocks and pieces of an old wetsuit  keep the battery from rattling against the plastic case as well as centered.  A 1 amp inline fuse is installed as per the manufacturers specs. The connecting plug (same as the one on the exterior cord) allows me to remove it from the case for charging. I have a matching plug installed on the charger cord. The plugs, terminal connectors, and fuse are from an auto parts store. I used heat shrink casings on the wires to seal them. The charge in the battery lasts for months. I store the battery behind my truck seat, along with my anchor and weight belt, so as not to have to carry them upstairs to my condo. Be sure to test the fish finder before launching. Rinse the exterior of the battery case as well as the transducer and fishfinder  after each dive. 

Carrying Case

Keeping the entire setup in a soft beverage cooler makes for easy carrying and storage. It also allows for it to be easily taken along in your vehicle whether you choose to use it or not.