How to Install a Side-Arm Transducer Mount on a Sit-on-Top Kayak

I bought my first Garmin Striker on a Friday in spring 2019 and spent the next Sunday standing over the deck of a new Old Town Topwater with a drill in my hand, trying to talk myself into making the first hole. I didn't make it. Put the drill down, walked away, went looking for another way — and the side-arm rig I ended up with that weekend is the one I still use seven years and four kayaks later.

You don't actually have to drill anything. This guide assumes you have already chosen the removable side-arm route and want the install procedure: where to put the base, how to seal the existing factory holes, how deep to run the arm, and how to keep the cable from becoming a failure point.

Still choosing between side arms, transom brackets, scupper kits, and in-hull options? Start with the no-drill transducer mount buyer guide, then come back here once you know a side arm is the right category.

If you've never seen a side-arm mount deployed off a kayak deck, the video below is the cleanest no-drill walkthrough I've found — watch it first for the visual, then come back and use the steps below as your checklist.

Why drilling holes in your kayak is a bad idea

The biggest reason is leak risk over time. Even a careful drill-and-seal job degrades — marine silicone goes brittle, the deck flexes every time you load gear, UV slowly eats the bond at the edges. The hole I drilled in a buddy's Wilderness Tarpon 120 in 2020 started weeping at the edges the following spring; we resealed it twice before he gave up and glassed it over from the inside.

Second, warranty. Hobie, Old Town, and most major manufacturers void hull warranties the moment you drill through the gelcoat or plastic. If anything else on the boat fails in the next few years, you're paying out of pocket.

And resale takes a real hit. I can't give you a clean percentage — I've watched the same model sell for $200 less drilled vs un-drilled on local Facebook groups, but the variance is wide. The point is that a deck hole costs you more than it ever saves.

A no-drill mount lets you sell the kayak with the gear removed and the hull untouched. That alone often pays back the cost of the mount.

Before you install: confirm a side-arm is the right method

A side-arm transducer mount is the right install when you want the puck in direct water, need accurate water temperature, want to remove the arm for car-topping, or may move the fish finder between kayaks. It is the default no-drill setup for most sit-on-top fishing kayaks with factory tracks or unused accessory holes beside the seat.

Use a different guide if your goal is different:

• For a product comparison before buying hardware, use the no-drill transducer mount buyer guide.
• For a hidden 2D-only shoot-through-hull install, use the in-hull transducer guide.
• For a basic Garmin Striker 4 where duct seal may beat external hardware, use the Garmin Striker 4 no-drill mount guide.

Factory-hole compatibility checklist

Before opening the parts bag, confirm these five points on the kayak:

1. Mounting point: There is a factory gear track, StarPort pad, or unused bolt pattern within arm's reach of the seat.
2. Water clearance: The arm can hang outside the hull without hitting the paddle stroke, pedal drive, rudder line, or crate.
3. Cable path: The transducer cable can run to the head unit without being pinched under the seat frame.
4. Transport removal: The arm can pop off before roof-rack or trailer transport.
5. Loaded waterline: With you and normal gear in the kayak, the transducer face can sit 3-6 inches below the water surface.

Step-by-step: install a side-arm mount

Here's the full procedure once you have the parts in hand. The first time you'll spend longer hunting for the factory bolt holes than on the install itself; by the second kayak it's a quick job.

Parts you'll need

Step 1 — Locate your kayak's factory accessory holes

Flip the kayak on its side and look near the seat / behind the cockpit for unused factory-drilled holes (often plugged with rubber bungs or small bolts). These are designed for paddle keepers, deck accessory mounts, etc. They're already there — you're not drilling new ones.

Most modern fishing kayaks have 4–6 of these per side.

Step 2 — Apply sealant and mount the StarPort base

Lay a thin bead of removable marine sealant (3M 4000, not 5200) on the bottom flange of the StarPort. Press it down onto the factory hole pattern, align the bolt holes, and finger-tighten the M5 bolts from underneath. Once aligned, snug them with the Allen key — don't gorilla-torque, just firm.

⚠️ Use 3M 4000, not 5200. 4000 is removable; 5200 is permanent. If you ever want to swap the StarPort, 5200 will tear gelcoat / plastic chunks out with it. 4000 peels off clean.

Step 3 — Insert the telescoping arm

Slide the arm shaft into the StarPort socket. Twist 90° to lock it. You should feel a positive detent — that's the lock engaging. The arm should pivot freely on the StarPort base but not lift out without the release lever.

Step 4 — Attach the transducer puck

The arm's wet end has a universal transducer plate. Most transducers ship with a small bracket that bolts to this plate using #10 stainless screws (usually included in the puck packaging).

Bolt the transducer to the plate. Tighten until firm; over-tightening strips the plate threads.

Step 5 — Adjust depth and angle

With the kayak upright, deploy the arm fully and check that the transducer face is submerged at fishing posture (you sitting in the kayak with normal gear loaded). Adjust the telescoping length until the face is 3–6 inches below the waterline.

That's it. Power up your head unit and you should see clean bottom returns within seconds.

The parts I'd put in a cart today

For most anglers, the side-arm category wins on the axes that matter: removable, swappable, full sonar quality. Here's what I'd buy today, by category, in price order:

The base mount (deck pad)

You bolt this once and forget it. The arm clips into it.

• Railblaza StarPort HD ⭐ — universal factory-hole fit, $20
• Scotty 268 Side / Deck Mount — slightly cheaper, less rotation range, $15

The arm itself

The actual telescoping shaft that holds the transducer in the water.

• Railblaza Transducer Arm II ⭐ — 12" telescoping, anodized aluminum, $45
• YakAttack BlackPak Transducer Arm — sturdier but pricier, $55
• Scotty 141 Mighty Mount — heavy-duty option for bigger transducers, $40

Marine sealant (don't skip)

• 3M Marine Adhesive Sealant 4000 UV ⭐ — removable, UV-resistant, $9/tube

Don't buy

• Suction-cup mounts (they release in the sun)
• Magnetic mounts (they don't grab PE plastic)
• "Universal scupper" mounts under $20 (the cheap molded plastic fails in one season)

The detail that tripped me up on my first build was the sealant. I reached for 5200 because every marine forum calls it the "standard," and six months later I couldn't get the mount off without ripping plastic out of the deck. Use 4000 for anything you might want to relocate later. Save 5200 for through-hull penetrations you're committing to forever.

FAQs about kayak transducer mounting

See the question and answer block above for the most common questions we get on this topic.

If you have a question we didn't cover, email hello@yakrigged.com — we update this guide each spring with the questions readers actually ask.

What's next

Once your transducer is mounted, you still need to get power from the battery to the head unit without flooding the hatch. We covered that end-to-end in how to run wires in a kayak for a fish finder — same no-drill philosophy applied to cabling.

Part of our complete series. This install procedure is one chapter of the Kayak Fish Finder Setup: Complete Guide — the hub covers the full rig from head unit selection through cable routing, with the deep-dive linked at every step.

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Mounted a transducer in a way we didn't cover? Send us a photo at hello@yakrigged.com — interesting rigs get featured in the monthly newsletter.