How to Mount a Transducer on a Sit-on-Top Kayak (No Drilling Required)

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. There are three no-drill ways to mount a transducer on a sit-on-top kayak, and one of them is clearly the right choice for most anglers. This guide compares all three, walks through the install for the winner, and lists the parts I'd buy today.

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.

The 3 most common no-drill transducer mounting methods

Method 1 — The in-hull (bonded) mount

You glue the transducer to the inside of the hull with marine adhesive. Sound waves pass through the plastic to the water below. The technique is real and used by professional sport-fishing boats for decades.

Pros: Cleanest deck (no visible mount), zero drag, completely hidden from view, transducer is protected from rocks by the hull itself.

Cons: Loses side-imaging entirely (the signal scatters through hull plastic), reduces max depth range by 15–30%, and the bond is permanent. You can't change your mind in three years.

This is a real option but only for a narrow case (single-kayak, 2D-only fishing, multi-year commitment). We covered the bond procedure, the hull material compatibility (PE works, Kevlar doesn't), and the failure modes in detail in our shoot-through-hull guide.

Method 2 — The scupper hole mount

Sit-on-top kayaks have molded drainage holes ("scuppers") that pass straight through the hull. The scupper mount drops a transducer down through one of these holes, suspended a few inches below the hull.

Pros: Hidden under the seat, no deck real estate consumed, no drilling.

Cons: Three real problems that disqualify it for most anglers:

1. The transducer hangs below the hull, fully exposed. In shallow rocky water — exactly where bass and trout live — it's the first thing to hit a rock. A friend of mine destroyed a Garmin GT8HW-IF on the Shenandoah on a single dragged grounding; $80 puck, written off in one trip.
2. It blocks the scupper. Most scupper mounts seal around the hole and defeat the kayak's drainage. Water that lands on deck stays on deck, which is fine right up until you take a wave over the bow.
3. It's hull-specific. Most scupper mounts are designed around one or two kayak models; check the maker's compatibility list before you buy, and don't trust "universal" claims under $20.

Scupper mounts make sense on dedicated saltwater offshore kayaks (Hobie Outback, Wilderness Tarpon 140) fishing depths over 15 ft where the transducer never sees a rock. For everything else, skip it.

Method 3 — The over-the-side arm mount ⭐ (recommended)

A telescoping arm bolted to a deck pad that uses your kayak's factory accessory holes (the ones that came pre-drilled from the manufacturer for paddle keepers and accessory tracks). The transducer hangs from the arm into the water alongside the kayak.

Pros:

• Uses your kayak's existing factory bolt pattern, so you put zero new holes through the hull
• Transducer sits in clean water alongside the kayak, not behind hull plastic — same sonar quality as a transom mount
• Reads water temperature accurately (the in-hull method can't)
• The telescoping arm lets you drop the puck 4" deeper for stained water or raise it for shallow flats
• Whole assembly pops off the deck pad in a few seconds for car-topping
• Swappable between kayaks — I run the same arm on my Old Town and on a friend's Hobie

Cons:

• You'll feel the drag on long paddle days. It isn't huge, but at the 6-mile mark it's there; on a pedal drive you won't notice it at all.
• In heavy weeds the arm catches. Pull the quick-release pin and lift it out of the water before you tangle up.

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 silicone and mount the StarPort base

Lay a thin bead of marine silicone (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.