Catamaran-specific inspection points
A catamaran adds two hulls, a bridgedeck and a shared structure that need their own checks. Inspect both of everything, and compare the two sides.
Updated 2 min read
Key points
- Inspect the bridgedeck, its underside and the joins to both hulls.
- Both engines, both drives and both rudders get the full check. Compare hours and wear.
- Many catamarans have cored hulls, so moisture readings matter.
Structure
- The bridgedeck. Look for cracks in the underside, signs of slamming, and repairs. Fatigue shows up at the points where the deck meets the hulls.
- Hull-to-bridgedeck joints, inside and out. They carry loads in waves.
- Crossbeams and the bow beam, which carry the rig loads. Check the bolts, the bonding and any movement.
- Bulkheads bonded to the hull and the deck, with no cracks at the corners.
Hull construction
Many cruising catamarans use cored hulls. Take moisture readings and hammer-test both hulls, the decks, and the area around fittings. See Hull moisture readings and delamination. Check the watertight compartments forward and aft, and that the hatches seal.
Running gear on two sides
- Two engines: compare hours and wear. A large difference between the two suggests one has been used more, or replaced.
- Two sail-drives or shafts: diaphragms, seals, anodes. See The haul-out checklist and running gear.
- Two rudders joined by a linkage: play in each, wear in the linking bar or cables. See Keel, rudder and steering inspection.
- Daggerboards or keels: check the cases, the lifting gear, and signs of grounding.
Rig
A catamaran mast is stepped on the bridgedeck or on a beam. Check the support structure and the chainplates. See Standing rigging and spars: when replacement is due.
Systems
- Fuel, water and waste tanks in each hull, with the cross-connections. See Fuel tanks, gas installation, plumbing and holding tanks.
- Electrics split between hulls, including the generator and the battery banks. See Electrical system and generator.
- Trampolines, the stitching, and their lashings.
- Steps and transoms, which take wear from the dinghy and swimmers.
Ask for a surveyor who knows catamarans
A monohull surveyor may not know where multihulls fail. Ask for experience with the builder and the model, and ask for a sample report. See What a survey includes, and what a surveyor does not inspect.
Related guides
General information, not legal, tax or financial advice. Rules change; check your own case with a professional or ask us.