Which Seakeeper Do I Need? The Complete Sizing Guide (Models 1–4 and Beyond)

From our complete Seakeeper gyro guide — compare every model, see installed-cost ranges, and request a quote through certified installers.

Seakeeper publishes boat-length ranges for every model, but if sizing were as simple as length overall, their dealers wouldn't spend half their day on sizing calls. Length is the starting point — displacement, beam, how you boat, and where the unit can physically live in your hull decide the final answer.

Here's how to get to the right model before you ever talk to an installer.

The quick-reference chart

Above the 4, the line continues for larger vessels — the 10.5 for ~50–62 ft, the 14 for ~55–68 ft, the 16 for 60–69 ft (up to 50 tons), and the 18 for 65–75 ft boats up to 56 tons — all the way to units for 85 ft+ yachts. But the 1 through 4 cover the overwhelming majority of recreational refits, so that's where we'll focus.

What each model is actually for

Seakeeper 1 — the entry point (23–30 ft). Built specifically to bring stabilization to small boats. It runs exclusively on 12V DC power — no generator needed — features a flush-mount design for easier installation, and can be installed virtually anywhere on board. One wrinkle worth knowing: without the optional Deck Mount Enclosure, the Seakeeper 1 must be installed in a covered location (enclosed leaning post, bilge, or console) to protect it from salt, water, and sun. The enclosure option opened it up to boats with open-framed leaning posts. Typical buyer: 24–28 ft center console, outboard powered, family or fishing use.

Seakeeper 2 — the volume seller (30–36 ft). The sweet spot of the recreational market, because 30–36 ft is where so many serious center consoles and small cruisers live. Still 12V DC, still generator-free, at 414 lbs. If your boat is 30–33 ft, this is almost always the answer. At 34–36 ft, you're in the judgment zone (more below).

Seakeeper 3 — the refit favorite (35–41 ft). The model Seakeeper calls its "biggest smallest thing," with a leaning-post installation option that has made refits dramatically easier on boats that were never designed for a gyro. Runs on 12V DC. If you own a 36–40 ft sportfish or express and the boat wasn't factory-prepped, the 3's flexible install options are likely why your quote is feasible at all.

Seakeeper 4 — the new flagship of the small range (38–44 ft). The 4 and 4.5 showcase Seakeeper's latest engineering — the most efficient and most effective gyrostabilizers ever built in their size range. At 746 lbs it's a serious structural commitment, sized for boats where the 3 would be working too hard.

The judgment zones — when you're between models

The length ranges overlap on purpose (30 ft fits the 1 and the 2; 38–41 ft fits the 3 and the 4). Here's how dealers actually break ties:

Displacement beats length. A heavy 30-footer (full tower, full fuel, quad outboards) rolls with more energy than a light 32-footer. When your boat is at the top of a model's range AND heavy for its length, size up.

How you boat matters. If you mostly run and gun, the smaller unit at 80% effectiveness may be fine. If you sit on anchor or drift all day — when roll is worst and the gyro works hardest — buy the unit rated for your boat with headroom.

One big unit vs. adequate. Seakeeper's own sizing tool (enter your boat, get a recommendation) is the official answer, and certified installers will confirm against your actual displacement. When in doubt between two models, the consistent dealer advice is: undersized gyros disappoint, correctly sized ones delight. Nobody has ever complained their boat was too stable.

The constraint nobody checks first: where it lives

Before you fall in love with a model, confirm it physically fits. The Seakeeper 2's envelope is roughly 25 x 26 x 20 inches and 414 lbs — and on many boats the honest question isn't "which model" but "where would it even go?" The unit must mount to structure tied into the stringers, with service access.

Refit locations, best to worst: factory Seakeeper-ready space (ideal), enclosed leaning post (the 1 and 3 were designed for this), console interior, bilge/lazarette (watch service access), custom structure (adds real install cost).

This is also why the install quote varies so much between identical boats — the unit price is fixed; the carpentry isn't.

Power: the question behind the question

The reason "which Seakeeper" matters so much for boats under 40 ft is power. The 1, 2, and 3 run on 12V DC — battery power, no generator — which is what brought stabilization to outboard boats in the first place. Expect a draw in the 300–600 watt range depending on model and sea state. The practical checklist:

• House bank of at least 200–300Ah usable (lithium strongly preferred for refits)
• Charging capacity to replenish overnight draws
• If your electrical system is original to an older boat, budget the upgrade into the project

(If you're already planning a lithium/Victron house-bank upgrade, doing it alongside a Seakeeper install is the efficient sequence — one yard visit, one electrical plan.)

Common sizing mistakes

Buying the 1 for a heavy 29-footer to save $8,700. The price gap between the 1 and 2 tempts everyone. If your boat is at the top of the 1's range with a tower and full offshore load, the 2 is the right call.

Ignoring future repowers. Adding heavier four-strokes or a second station changes displacement. Size for the boat you're building, not the boat you bought.

Letting the install location pick the model. "The 1 fits in my console, so I'll buy the 1" on a 34-ft boat produces an underwhelming result. If the right model doesn't fit anywhere, the honest answers are structural work or Seakeeper Ride — not the wrong gyro.

Frequently asked questions

Can I put a bigger Seakeeper than recommended on my boat?

Generally unnecessary and sometimes counterproductive — weight, draw, and cost rise fast. Match the rating; don't double it.

Do I need a generator for any of the 1–4 models?

No — the small-range units run on DC power, which is their defining feature. Larger models up the line have different power requirements.

What about catamarans and pontoons?

Cats roll far less by design and are rarely gyro candidates. For pontoons, Seakeeper Ride (not the gyro) is the system now entering that market.

My boat is 41–44 ft — 3 or 4?

This is the classic judgment zone: the 4's newer engineering and headroom usually win for heavy sportfish use; a lighter express at 41 ft can be well served by the 3. This is exactly the call a site visit settles.

Get a sizing recommendation for your exact boat

Charts get you close. Your hull's displacement, layout, and electrical system get you the real answer.

Request a Seakeeper sizing consult Send your boat make, model, year, and power, and we'll connect you with a certified installer who'll confirm the right unit and quote the install — before you spend a dollar.