Hull and structure
Bulkhead
A wall across or along the inside of a boat, bonded to the hull and deck, that stiffens the structure and often carries rig or engine loads.
Cored hull
A hull or deck built as a sandwich: two skins of fibreglass with a light core of balsa, foam or plywood between them.
Delamination
Layers of a fibreglass laminate coming apart, or a cored panel's skins separating from the core, which costs the panel its stiffness and strength.
Gelcoat
The thin, hard, coloured resin layer on the outside of a fibreglass boat, which gives the shiny finish and keeps water off the laminate behind it.
Hull-to-deck joint
The seam where a fibreglass deck is fastened and sealed to the flange of the hull, usually hidden under the toe rail or rub rail.
Keel bolts
The bolts that hold a bolted-on ballast keel to the hull, passing up through the hull bottom to nuts and backing plates in the bilge.
Osmosis
Water getting into a fibreglass hull through the gelcoat and reacting with the laminate, which shows as blisters on the underwater hull.
Stringer
A long stiffener bonded along the inside of the hull bottom, fore and aft, that keeps the hull from flexing and usually carries the engine mounts.
Tabbing
Strips of fibreglass laid over the joint where a bulkhead or stringer meets the hull, bonding it in place.
Transom
The flat, aft-facing surface across the stern of a boat, which on many powerboats carries the outboard or sterndrive and, by US rule, the hull identification number.
Underwater gear
Anode
A block of zinc, aluminium or magnesium fitted to a boat's underwater metal that corrodes in its place, so the propeller, shaft and fittings last.
Cutless bearing
The rubber-lined bearing in the strut or stern tube that supports the propeller shaft just ahead of the propeller, lubricated by the water it runs in.
Dripless shaft seal
A seal where the propeller shaft leaves the hull that stays dry by pressing a carbon or graphite face against a stainless collar, held by rubber bellows.
P-bracket
The bracket that holds the propeller shaft out in the water just ahead of the propeller, carrying the cutless bearing.
Saildrive
An engine and drive leg built as one unit, with the leg passing down through a large opening in the hull that's sealed by a rubber diaphragm.
Seacock
The valve bolted through the hull that opens and closes an underwater opening, so water can be shut off if a hose or fitting below the waterline fails.
Sterndrive
A drive leg bolted to the outside of the transom and driven by an inboard engine through it, steering by turning the whole leg.
Sterndrive bellows
The rubber boots that seal the drive shaft, shift cable and exhaust passages where a sterndrive goes through the transom.
Stuffing box
The packed gland where the propeller shaft leaves the hull, sealed with rings of packing that drip a little seawater onto the shaft to cool and lubricate it.
Through-hull
A fitting that passes through the hull to let water in or out, such as an engine intake, a sink drain or a transducer, usually closed off by a seacock.
Rig
Chainplate
The metal strap bolted to the hull or a bulkhead that a shroud or stay attaches to, carrying the rig's load into the boat's structure.
Mast step
The fitting the bottom of the mast stands on: on deck for a deck-stepped mast, or low in the hull above the keel for a keel-stepped one.
Roller furler
A drum, foil and top swivel on the forestay that let you roll the headsail away round the stay from the cockpit.
Standing rigging
The fixed wires or rods that hold a sailboat's mast up, the shrouds at the sides and the stays fore and aft, with their terminals and turnbuckles.
Swage terminal
A stainless fitting pressed onto the end of a rigging wire by a machine, which connects the wire to the mast or the turnbuckle.
Engine and fuel
Anti-siphon valve
A small valve at the top of a petrol tank's fuel outlet that stays closed unless the engine's fuel pump is drawing, so a broken fuel line can't siphon the tank into the bilge.
Diesel bug
Bacteria and fungi that grow where water meets diesel in a fuel tank, forming slime that blocks filters.
Engine mounts
The rubber-and-steel blocks that hold an engine to its bearers and absorb its vibration.
Exhaust riser
The raised section of a marine inboard's exhaust that keeps seawater from running back into the engine and brings the cooling water into the exhaust.
Mixing elbow
The fitting on a marine engine's exhaust where the cooling water is sprayed into the hot exhaust gas, so the exhaust hose can carry both out of the boat.
Water pump impeller
The flexible rubber rotor that pumps cooling water from outside the boat through an engine.
Electrical
Battery management system
The electronics that watch a lithium battery's voltage, current and temperature and disconnect it before it's damaged.
Battery switch
The heavy rotary switch that connects or isolates a boat's batteries, often marked 1, 2, Both and Off.
Bonding system
Wires, usually green, that connect a boat's underwater metal fittings to each other, the anodes and the DC negative.
ELCI
A breaker on a boat's shore power that trips when current leaks out of the AC system, usually at 30 mA, so the boat can't put dangerous current into the water.
Galvanic isolator
A device in the shore power earth wire that blocks the small DC currents that corrode a boat's underwater metal, while still passing fault current so the earth stays safe.
Reverse polarity
A shore power fault where the hot and neutral wires are swapped, so breakers switch the neutral and leave circuits live.
Stray current corrosion
Fast corrosion of an underwater fitting caused by an electrical leak pushing current through it into the water.
Plumbing and tanks
Bilge pump
An electric or manual pump that removes water from the lowest part of the hull, usually started automatically by a float switch when water rises.
Holding tank
The tank that stores toilet waste on board until it can be pumped out ashore or discharged where it's allowed.
Vented loop
A loop in a hose run above the waterline with a small vent at the top, which breaks the siphon so seawater can't flow back in through a discharge or intake.
Gas and safety
CO detector
An alarm that warns of carbon monoxide from engines, generators and fuel-burning appliances in a boat's living spaces.
Gas locker
A vapour-tight locker for LPG cylinders that drains overboard, so leaked gas goes over the side and can't sink into the bilge.
Life raft service
The periodic unpacking, inflation test and repacking of a life raft by an approved station, recorded on a label and certificate.
Survey terms
Condition and valuation (C&V)
A boat survey that reports the boat's condition and ends with the surveyor's opinion of its market value, often asked for by insurers and lenders.
Haul-out
Lifting a boat out of the water, usually in a travel hoist, so the surveyor can inspect and sound the hull below the waterline.
HIN
The 12-character number moulded or fixed on a boat's transom that identifies its builder, serial number and build and model year, like a car's VIN.
Limitation period
The time after a survey within which a client can bring a claim. In England and Wales it's generally six years for a claim in contract.
LOA, beam and draft
A boat's three main dimensions. LOA is its length from end to end, beam its greatest width, and draft how deep it sits below the waterline.
Moisture meter
A hand-held meter that a surveyor presses against a fibreglass hull or deck to compare moisture levels across it, finding wet laminate and wet core.
Port risk
Insurance terms under which a boat is covered only while in port or ashore. NAMS advises surveyors to recommend it in bold when they find a boat unseaworthy.
Professional indemnity insurance
Insurance that pays a surveyor's legal costs and any damages if a client claims the survey was negligent. IIMS requires its small craft surveyors to hold it.
Sea trial
The part of a boat survey where the boat is taken out and run under power, and under sail if it has one, to see how the engine and systems behave under load.
Terms of reference
The written instructions agreed with a client before a survey: who the client is, the purpose, what will and won't be inspected, and who may rely on the report.
European paperwork
Brodica
The Croatian term for a boat over 2.5 m up to 15 m, registered and inspected by the harbourmaster; craft over 15 m are yachts surveyed by the Croatian Register of Shipping.
Certificado de navegabilidad
The Spanish certificate that a recreational boat meets the rules, recording each compulsory inspection and the date of the next one; it must be kept on board.
Certificat d'enregistrement
The single French registration document for pleasure craft that replaced the carte de circulation and the acte de francisation.
DAFN
France's annual tax on pleasure craft, now called the taxe annuelle sur les engins maritimes à usage personnel, based on hull length and engine power.
Declaration of conformity
The builder's signed statement that a recreational boat meets the EU Recreational Craft Directive, which must accompany the craft.
DEKPA
Greece's Pleasure Craft Traffic Document for recreational boats; issuing or attesting it requires that month's TEPAI to be paid.
Design category
The A, B, C or D rating on a CE boat's builder's plate, stating the wind and wave conditions it was designed for.
Flaggenzertifikat
A certificate from Germany's BSH for seagoing pleasure boats up to 15 m, valid for eight years, that isn't proof of ownership.
Gewährleistung
The German statutory warranty on a sale, two years from handover, which a private seller can exclude in writing and a dealer can shorten to one year on a used boat.
ICP
A document from KNMC or the Watersportverbond that Dutch boat owners use to prove ownership on inland and coastal waters in a list of European countries. It isn't proof of nationality.
Internationaler Bootsschein (IBS)
A German boat document issued by the DSV, the DMYV or the ADAC, renewed every two years and widely used as proof of ownership, though no authority issues it.
ITB
The common name for Spain's compulsory inspections of recreational boats under Real Decreto 1434/1999, done by accredited inspection bodies and recorded on the certificado de navegabilidad.
Kadaster
The Dutch land and ship registry, where registering a boat establishes its ownership and lets a mortgage be recorded against it.
Lista 7
The list in the Spanish ship register for private recreational boats; lista 6 is for boats used commercially, such as charter boats.
Natante
The Italian category for pleasure craft of 10 m or less, which don't have to be registered; imbarcazioni run to 24 m and navi da diporto are larger.
Part 1 registration
The part of the UK Ship Register for pleasure and commercial boats that records ownership and lets a marine mortgage be registered against the boat.
Small Ships Register (SSR)
Part 3 of the UK Ship Register: a low-cost register for UK-resident owners' pleasure boats under 24 m that proves nationality abroad but doesn't record ownership.
TEPAI
Greece's monthly fee on recreational boats over 7 m in Greek waters, whatever their flag, paid through AADE's eTEPAI application.
Transit log
The customs document foreign private yachts over 7 m file in Greece to cruise Greek waters, now issued online through myAADE.
Zeebrief
The Dutch certificate of registry for seagoing vessels, issued by ILT as proof of nationality and the right to fly the Dutch flag, which becomes invalid when the boat is sold.