By Paul Lebowitz

For those of us who fish waters over knee deep, adding a fishfinder to our kayaks provides a wealth of information. More accurately called sonars, fishfinders are most useful for finding the structures that hold fish. The basic data provided by a fishfinder is water depth. If we pay attention to the fishfinder while we are moving from place to place, we can pinpoint productive structures such as drop-offs, holes, and rock piles. After a bit of practice the jumbled squiggles on screen start to make more sense, allowing us to discern whether the bottom is soft sand, vegetation, or rock. Fishfinders may also be used to identify bait fish schools, thermoclines, or somewhat less reliably, individual gamefish. 

A kayak is a tough environment for a fishfinder. Proximity to the water’s surface subjects our electronics to constant spray and splash.

In particular, the salt left behind by evaporating saltwater causes damaging corrosion. I want my fishfinder to work when I turn it on, so I called Mr. Luke Morris, Senior Technical Representative for Lowrance Electronics to ask what kayak anglers can do to take care of our electronics.     

According to Morris, fishfinders require very little maintenance. They are designed to survive the demanding marine environment. The only difference between fishfinder use on a boat or a kayak is the increased chance of submersion on the kayak. Most sonar heads (the display and processing units) are waterproof. Lowrance and Eagle sonars are designed to survive immersion in one meter of water for up to an hour.

There is a weak link. Most fishfinders have detachable power and transducer cables. The cables and sonar head are joined by pins on one side and a socket on the other. The pins are delicate. If exposed to saltwater they quickly corrode. A thin layer of dielectric grease will protect the metal. It isn’t necessary to pack the connectors with grease. Morris says most people apply too much. Spread just a bit of grease onto the flat face of the socket. Don’t mound it up like you are icing a cake. Use just enough to put a small amount of grease over each socket hole. Then connect each cable to the sonar head. The fragile pins will pick up just the right amount of protective grease.

Once we have learned how to prevent corrosion on the electrical contacts, Morris advises us to turn our attention to the cable connectors themselves. Usually the ends of the cables have locking mechanisms and / or watertight or waterproof seals. Unfortunately just a couple of hours of splash and spray can leave enough salt buildup on the connectors that detaching the cables from the sonar head becomes difficult. Don’t force them open! Forcing the cable locking mechanisms is a good way to bend or break the fragile electric pins, and then you are out of luck. Sticky connectors are easy to fix. A quick rinse with a gentle flow of fresh water, while the cables are attached to the sonar head to protect the pins, should wash away the salt and sand or other debris and restore the locks to easy operation.  

Once the connectors are dry check out the moving parts of the cable locking mechanisms. If the connectors have a visible seal it is a good idea to lubricate it once in a while. A bit of grease strategically placed will keep the water out, further protecting the pins and keeping the connectors easy to use. Again, avoid applying too much grease.

It is hard to do much else to harm contemporary fishfinders. The pins are unlikely to break or bend as long as the connectors are maintained. A tumble in the surf might defeat the waterproofing that protects the sonar head, ruining the processor. Otherwise use common sense. For instance, fishfinder cables are poor handles for pulling or lifting a kayak. If your fishfinder breaks call the manufacturer. Most fishfinders can be repaired by the factory for less than the cost of a new one.