DIY Portable Fishfinder For Your Kayak

I have been asked quite a few times recently about my fish finder setups and what I would recommend as far as units and mounting are concerned.  When I wrote for Examiner.com I published a basic “how to” article on making a removable system.  Instead of linking back to Examiner, I decided to park the write-up here with a few updates.

Backlight on the Humminbird Piranhamax

As far as units go, I have a Cuda 242 permanently mounted on one of my Big Game’s and a Piranhamax 160 on a removable setup that I use on my girlfriend’s tarpon 140.  Whenever I head to Virginia, I take the removable unit and use it on my Big Game that I keep at my family’s house.  Both are great basic fishfinders, but the Piranhamax has a better LED backlight system if you plan on fishing at night.  If I ever have to replace either unit, I will probably take a hard look at some of the higher end color units that have more features.  But if you want a great fishfinder at an exceptional price, the Cuda series from Eagle and the Piranhamax line from Humminbird are excellent contenders in the sub $100 range.

The technology housed in the most basic sonar unit can be a real asset to the kayak fisherman. Modern units are waterproof, energy efficient and can be powered by a variety of different battery options. This write up will focus on the basic guidelines used in the construction of a removable, all in one, portable assembly that even a novice do-it-yourselfer can put together in a few hours. 

The unit pictured in this article, the Humminbird Piranhamax 160, retailed for $89 at the West Marine in July of 2010.   The newer Piranhamax 170 is currently available for $79 at a number of different retailers local and online. Aside from the basic sonar functions, this model includes a water temperature sensor and a 5 stage adjustable backlight setting. I called Humminbird and was reassured the unit operates on a power input range of 10 to 20 volts.  This is nice because it gives a lot of flexibility when considering how to power the unit.  Since portability is the objective, 12 NiMH rechargeable “AA” batteries wired in a series (diagram can be seen HERE) were chosen to power the unit. Each of the rechargeable “AA” batteries supplies 1.2 volts (as opposed to standard, non rechargeable “AA”s that deliver 1.5 volts) for a total of 14.4 volts when wired in a series. The 12 rechargeable batteries will power the unit for more than 8 hours of continuous use.

The basics components of the mounting assembly are listed below:

Lowes:

A length of ½” schedule 40 PVC pipe

(1) - Weatherproof Round Blank Plastic Cover (electrical aisle)

(2) - ½” “T” PVC slip fittings

(1) - ½” 90 degree elbow PVC fitting

(2) – ½” PVC plug (flat portion to which the round black cover is bolted to the PVC assembly)

Package of Velcro One Wraps 23" x 7/8" each (located at the end of aisles at Lowes)

(1) – 18 inch length of flat aluminum bar (bolt and screw aisle)

Various mounting nuts, bolts and screws – all stainless steel.

1 ½” diameter ABS black plastic tube, cap & screw on fitting (for battery housing, located in the PVC aisle)

(1) – small jar of PVC glue 

(1) – tube of silicone sealant
(1) – tube of Loctite thread locker

Radio Shack:

(3)– 4 AA battery holder

(1) – package of heavy duty snap connectors

Since each application is different, use the pictures as a guide to construct your own setup. I selected a Scotty Triple Rod holder for the base of the mount, but a standard single Scotty mount receptacle will work just fine too with a little creativity. The triple mount provides a very solid platform to mount all of the components and leaves one mounting hole open for other accessories. All the white PVC parts are glued together except for the horizontal piece that slides into the 90 degree fitting. Leaving one end of the arm unglued allows the transducer arm to swivel up and out of the way in shallow water.  Glue the flat PVC cap into the "T" fitting and drill a hole through the center of the gray round plastic disk and the end cap. Attach the two pieces with a large bolt and nut (use Loctite on the threads).  Using the included hardware, attach the fishfinder to the gray plate as pictured above.  Cut two small lengths of PVC tubing and glue them into the down ends of the "T" fittings.  These pieces fit snuggly into two holes of the Scotty triple mount and lock the whole assembly in place.

The picture above gives a clearer illustration of how to wire up the unit. The positive (+) wire from one holder is soldered to the negative (-) wire on the next battery holder.  When all three holders are wired in a series, solder the remaining positive and negative wires to the power cord supplied with the fishfinder.  Each battery assembly slides into the black ABS plastic tube. Apply silicone sealant around the power wire where it exits through the battery tube to ensure a watertight assembly.

Bend the end of the aluminum bar at a 90 degree angle and mount the transducer to it using stainless steel nuts and bolts. Be sure to apply Loctite to the threads to ensure a semi-permanent bond. Slide the other end of the bar inside the vertical portion of the PVC pipe, drill a hole through both sections and bolt into place. Attach the transducer wire to the arm with Velcro and wrap the excess transducer cord around the black ABS battery tube. Secure the wrapped wire to the battery tube with 2 Velcro straps. Lastly, attach the battery tube to the horizontal PVC arm with the remaining straps until a solid connection is made.

I have been using this setup for just about a year now and it still works great.  If I were to change anything, it would be to add a cotter pin or something similar to the PVC arm that swivels up and down.  It still works just fine as-is, but the cotter pin would allow for it to lock in an upward position a little more securely.