How to buy a catamaran — the complete guide

A cruising catamaran buys you something no monohull can: a level, spacious platform that barely heels, sails flat and fast, and gives a couple or a family the deck space of a boat 15 feet longer. But a cat is two of everything — two hulls, two rudders, two engines — held together by a bridgedeck that is the most structurally demanding part of the boat. Buy the right one and you have the finest live-aboard cruiser afloat. Buy a tired ex-charter cat with a hard life, and you buy two of every problem.

Who a catamaran is for

Catamarans suit cruisers who value living space, stability and shoal draft over the pointing ability and cheaper berthing of a monohull. If your plan is a couple or family living aboard, island-hopping the Caribbean, the Bahamas, the Med or the South Pacific, a cat is hard to beat: it sits flat at anchor, has a huge cockpit and saloon on one level, sleeps a crowd in separate hulls, and its shallow draft lets you tuck into anchorages a keelboat can't reach. Guests who get seasick on a heeling monohull are often fine on a cat.

They are less ideal if you want to sail hard to windward in a blow, keep the boat on a tight budget, or berth in a crowded marina — a cat's beam means premium slip fees and fewer available spots. And a cat's motion, while flat, can be a quick, jerky "hobby-horse" in a short chop rather than the long roll of a monohull. Know which trade-off you're buying.

What to look for when buying

Why cats cost more — and hold value. You are buying two hulls, two engines, two saildrives, two rudders, often two of each system. That's why a comparable-length cat costs far more than a monohull, and it's also why good cats hold their value well: demand for quality bluewater cats consistently outstrips supply, and a well-kept boat resells strongly. Budget for the doubling on the way in and enjoy it on the way out.

Bridgedeck clearance and slamming. The bridgedeck is the structure spanning the two hulls, and the gap between its underside and the water is the single most important number on a cruising cat. Too little clearance and waves slam the underwing at anchor and underway — an exhausting bang that also stresses the structure over years. Sight the clearance, ask the designed figure, and treat generous clearance (and a fine, wave-piercing nacelle rather than a flat pan) as a real quality marker. A boat that slams badly is one you'll grow to hate.

The structural inspections unique to cats. Because a cat has no ballast keel and instead relies on its beam and a stiff bridgedeck for strength, the load paths are different from a monohull and the failure points are specific:

• Hull-to-deck joint. On a cat this joint runs an enormous length and carries real load. Look for weeping, crazing, sealant failure or any sign of movement, inside and out.
• Bulkhead tabbing. The bulkheads tie the two hulls to the bridgedeck. Detached, cracked or "clicking" tabbing — especially the main forward and mast-step bulkheads — is a serious, expensive finding. Check where you can reach, and have the surveyor sound the rest.
• Keel / daggerboard trunks. Whether the boat has stub keels or daggerboards, the trunks and their surrounding laminate take grounding and side loads. Look for cracking, delamination and water intrusion around the trunks and board cases.
• Signs of a previous grounding. Cats ground more easily because they draw so little and get pushed into thin water. Look for repaired or fair-but-suspicious keel bottoms, disturbed gelcoat, and internal cracking near the keel roots.
• Bridgedeck stress cracks. Gelcoat crazing radiating from the forward bridgedeck, cabin windows, and the underwing forward beam can signal slamming fatigue or overload. Distinguish cosmetic gelcoat cracks from structural ones — a surveyor's moisture meter and a good torch tell the difference.

Twin diesels and saildrives. Most cruising cats drive through saildrives rather than shaft-and-strut, and saildrives carry their own maintenance discipline. The rubber diaphragm that seals the leg through the hull is a wear item on a service interval (typically around every seven years or per the maker) — a failed diaphragm can sink the boat, so confirm it's been done and dated. Inspect the saildrive legs for galvanic corrosion: pitting, chalky white aluminium, and eaten anodes. Verify the anodes are fresh and the boat has been on a working galvanic-isolation or bonding setup, because a cat sitting in a marina with poor isolation eats its saildrive legs alive. Run both engines, check both gearboxes, and look at hours — they are often unequal.

Weight loading — this matters hugely on a cat. A catamaran's performance, motion and even its safety are exquisitely sensitive to weight. Overload a cat and it settles, the bridgedeck clearance drops, it slams more, sails slower and points worse. An owner boat crammed with years of gear, oversized battery banks, watermakers, generators, dive kit and full tanks can be floating well below its lines. On inspection, sight the actual waterline against the designed one, ask what's aboard, and be wary of a boat that's been "improved" into obesity. Conversely a lightly-loaded, well-optimised owner boat is a joy — spotting the difference is a real skill worth developing.

Ex-charter vs. owner-version. A large share of the cats on the market came out of charter fleets, and the trade-off is real. Ex-charter pros: cheaper for the length, simple robust systems, well-documented service, and charter-spec four-cabin layouts sleep a lot of people. Cons: high engine and sail hours, hard use by inexperienced crews, groundings, thin equipment (basic electronics, no watermaker, minimal ground tackle) that you'll spend to upgrade, and a "phase-out" boat that a fleet was happy to shed. An owner-version (often a three-cabin "maestro" layout with an owner's hull) is usually better-equipped, better-loved and lighter-used — and priced accordingly. Neither is wrong; just buy the charter boat with eyes open and price the refit in.

What it costs to own

Plan realistically before you fall in love with a listing. A cat's beam means you pay a premium at the dock — many marinas charge catamarans around 1.5x the standard slip fee, and some charge full double, so berthing is a materially bigger line than for a monohull of the same length. Insurance runs higher too, driven by hull value and the intended cruising area (offshore and hurricane-zone coverage costs more and comes with conditions). As a rough planning figure, budget roughly 8–12% of the boat's value per year for all-in ownership — berth, insurance, haul-out and antifoul (two hulls to paint), servicing, and a reserve for the inevitable. Maintenance is genuinely doubled on the mechanical side: two engines, two saildrives, two of most through-hulls. Fuel, on the other hand, is modest — cruising cats motor economically at sensible revs, and many owners burn less than expected because they actually sail. The good news at the far end: quality cats stay liquid, so resale is easier and stronger than for most boat types.

New vs. used / buying direct

New cats command long waitlists and a hefty premium, and depreciation is real in the first few years — which is exactly why the sweet spot for most buyers is a well-kept boat three to eight years old, where someone else absorbed the initial drop and the boat is proven. Used charter boats phase out on a predictable cycle and flood certain markets seasonally, which can be an opportunity if you price the refit honestly. Buying direct from an owner cuts the broker commission entirely — meaningful money on a half-million-dollar boat — and, just as valuable, it puts you in direct contact with the person who actually maintained her. Ask for the service records, the saildrive diaphragm dates, the anode history, and why they're selling. On HulloShips you deal with that owner directly; use /services/ to line up an independent survey, finance and transport, and /atlas/value/ to sanity-check the asking price against real market data before you make an offer.

A pre-purchase checklist

• Measure or confirm the bridgedeck clearance; ask about slamming at anchor and underway.
• Inspect the full-length hull-to-deck joint for weeping, movement and sealant failure.
• Sound and sight the bulkhead tabbing, especially forward and at the mast step, for detachment or cracks.
• Check keel / daggerboard trunks and board cases for cracking, delamination and water intrusion.
• Hunt for evidence of a previous grounding — faired repairs, disturbed gelcoat, internal cracking at the keel roots.
• Look for bridgedeck stress cracks radiating from the forward underwing and window corners; separate cosmetic from structural.
• Confirm the saildrive diaphragm service is done and dated on both legs; failed diaphragms can sink the boat.
• Inspect both saildrive legs for galvanic corrosion; verify fresh anodes and a working isolation/bonding setup.
• Run both engines to temperature; compare hours, check both gearboxes, exhaust and mounts.
• Sight the actual waterline vs. designed; assess whether the boat is overloaded and inventory what's aboard.
• Establish the boat's history: owner-version or ex-charter, hours, groundings, and full service records.
• Check the rig, sails and standing rigging age; a cat loads its rig hard and re-rigging is a significant cost.
• Test all systems dockside and, ideally, on a sea trial under sail and power before you commit.
• Commission an independent surveyor experienced specifically with multihulls — monohull surveyors miss cat-specific faults.

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