Projects To Improve Your Boat


How To Install A Fishfinder

By Lenny Rudow
Published: June/July 2012

Take on this simple electronics installation, and you’ll see what lies beneath your boat.

Whether you're a diehard angler, a casual fisherman, or a weekend cruiser, you probably have or would like to have a fishfinder onboard, so installing or replacing a fishfinder is a job you’ll probably tackle sooner or later. Lucky for us, when it comes to binnacle-mounted units that use transom-mounted transducers — the most common fishfinder installations on the water — this is an easy DIY job you can handle. All you need are a few tools and the know-how, which you'll find right here on these pages.

Illustration of Fishfinder installation

Step I: Installing The Binnacle Mount

Before you begin this mounting job, you'll need to find the best location. Try to keep the fishfinder as close as possible to center on the helm, which provides the best viewing angle. The unit should be between waist- and shoulder-high; stay away from overhead mounting locations such as in an electronics box or hanging down from a hard-top, which will force you to crane your head back when using the unit and may lead to neck strain. Also, make sure the location allows you to tilt and/or turn the unit without hitting the windshield, throttle, compass, or other affixed items.

Inspect the helm station from the back or underside, to ensure the area underneath is clear of obstructions, and has sufficient room for protruding bolts and wires. This is also a good time to locate the power bus and/or fuse block, and make sure you have terminals available for use; ABYC specs allow for up to four terminals per stud. Once you've chosen the location, either use the binnacle template included with the fishfinder, or use the binnacle itself as a template, to mark the location of the mounting holes with a pencil. Drill out the mounting holes with your power drill, running it at full speed at all times (a slowly turning drill bit is more likely to catch the gelcoat's edges, causing it to splinter and chip).

Now you need an entry/exit point for the unit's wires. Before you drill one out, inspect the console to make sure there isn't already a hole from a prior gear installation, which you can re-use — the fewer holes in your helm, the better. Assuming you don't get off so easy, you will need to drill a hole directly behind the binnacle mount. Make sure it's large enough to accept all of the unit's wires, and before you drill, put the binnacle and fishfinder temporarily in place to ensure there's enough clearance between the mount and the hole for the wires to pass through, without making any sharp bends. Otherwise, the wires might rub against the edge of the hole and chafing could become a problem down the road.

With all holes drilled, run a bead of silicon sealant around the base of the binnacle mount and around each hole. Put the binnacle in place, and before running the bolts through, give each a dab of silicon on their ends. Now secure the bolts to the helm with Nylock aircraft-style locking nuts.

Photo of positioning a fishfinder
First things first: Find the best location for your fishfinder.

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Tech Support

Degree Of Difficulty:
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  • Phillips-head screwdriver
  • Power drill and bit(s)
  • Wire crimper/stripper
  • Wire fish
  • Fishing rods (for testing your handiwork, after the installation is done)
 (with West Marine pricing):
  • 3M 5200 Adhesive/sealant $14
  • Adhesive-lined heat-shrink tubing $5
  • Cable ties $3
  • Clamshell fitting $3
  • Mounting hardware (usually included with fishfinder)
  • Silicon sealant $10
  • Crimp connectors $3
  • Terminal connectors $4
Project Cost
 (based on West Marine pricing):
Approximate Yard Time/Cost

This is a straightforward job and shouldn’t take a pro more than an hour or so. The national average cost for a marine electronics installer runs about $80 an hour but many have minimums, so you can plan on saving around $100 by doing the work yourself.

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