Catamaran survey checklist highlights critical multihull inspection points

Bridge-deck cracks, wet cores, and tired bulkheads can turn a clean catamaran closing into a painful walk-away. The first real test is not the cosmetics but the structure that keeps two hulls behaving like one boat, where lost leverage, insurance headaches, or a deal breaker begin. Even the name has roots in tied timber, from the Tamil word kattumaram.

Start on the hard, where expensive mistakes show up first

The out-of-water inspection is where a buyer earns real negotiating power. The Catamaran Gurus checklist puts the obvious damage and the hidden damage side by side: blisters, cracks, soft or hollow spots, scratches and chips, moisture readings, osmosis, propeller and shaft condition, thru-hulls, keel or centerboard hardware, rudder condition, sensors, and cathodic protection. A cat that looks clean from the dock can still be carrying repair costs below the waterline, where yard labor and haulout time quickly add up.

A proper haulout belongs in the budget. Owners or buyers usually pay the lift-out fees and often book a power wash so the submerged surfaces can actually be inspected. That is the point where a stained prop shaft, corroded zincs, or a suspect thru-hull shifts from a small maintenance note into a conversation about what comes off the asking price.

Do not let the bridge deck fool you

Catamarans live and die by their load paths, and that makes the in-water structure more important than the shiny topsides. The checklist widens the lens to topsides, deck molding, coachroof, cockpit, hull-to-deck joint, and especially bulkheads and structural stiffening, because bridge structures on multihulls are harder to read than the equivalent structure on a monohull. A thin-looking crack in a deck panel can be trivial, or it can point to a working joint, moisture in a core, or a collision of loads between the hulls.

A surveyor who simply glances at the hull sides is not enough. The stronger inspections include moisture testing of the deck and cockpit, plus opening floorboards and checking cabinets and bilges to find water migration that hides behind joinery. If the deck laminate is wet or the cockpit molding has soft spots, the issue is not just repair cost; it affects whether an insurer will accept the boat without more questions.

Treat bulkheads and rig loads as one problem

The main bulkhead near the mast is one of the most important pieces of structure on a catamaran because it ties both hulls and the main cabin together and helps keep the hulls from bowing outward or twisting in a cross sea. Lagoon 450 bulkhead problems that came to light in 2020 included cracks, warping, delamination, and partially bonded bulkheads and stringers.

The inspection has to get specific. Look hard at rigging attachment points, chain plates, mast step, shrouds and stays, winches, mast electrical, hatches, lifelines, and the steering system. The full pre-purchase survey to ABYC standards also reaches into standing and running rigging, sails, engine and mechanical systems, electrical systems to ABYC E-11, fuel and gas installations, and safety equipment.

Inspect the systems that have to work twice, not once

A monohull can sometimes limp through with one trouble spot. A catamaran doubles the systems burden, which means the survey has to test how well the two hulls are being maintained as a pair. Engine hours matter, but so do hoses, spare parts, bilges, water staining, rust and corrosion, and zincs, because every weak point in the machinery spaces gets multiplied when you are asking one hull to cover for the other.

The underbody and machinery list should also include propeller and shaft condition, rudder condition, keel or centerboard hardware, and any sensors that support navigation or systems monitoring. If the boat has duplicate equipment, the buyer needs to know whether both sides match in age and condition, or whether one hull has been quietly carrying the load while the other side has become the bargain you will pay for later.

Use a catamaran surveyor, not a generic one

Marine surveyors are supposed to be impartial and unbiased, and ABYC standards are meant to improve safety and reduce accidents. The right surveyor will understand multihull structure, not just hull polish, and will know when a bridge-deck issue is cosmetic and when it is evidence of load or water intrusion.

The Multihull Company makes the survey and sea trial the core of the purchase process. A written report usually arrives two or three days after the inspection, and deficiencies found there can become the basis for additional concessions from the seller.

Let the survey affect insurance before it affects your pride

Survey age can complicate coverage even after you think the purchase is done. SafeYacht Insurance typically expects surveys within two to five years for vessels above mid-five-figure values, and underwriters commonly look at hull condition and survey age.

A serious survey day may have the buyer, broker, surveyor, and sometimes the seller’s captain working around haulout availability. A thorough inspection may include climbing the rig.