Surveys
What Happens During a Marine Survey?
By The VesselBook Team · Published July 29, 2026 · 7 min read
A marine survey is a few hours of methodical inspection — hull and structure, deck and fittings, engine installation, electrical, plumbing, steering, and safety gear — usually with the boat hauled out so the underwater half can be seen, followed by a written report that lists what the surveyor found and what they recommend doing about it. On a typical recreational boat, expect the surveyor to be aboard for three to eight hours and the report to arrive within a few days to a week.
Nobody surveys a boat for fun. People order one because they are buying, because an insurer asked for one, or because something happened and they need it documented.
The three surveys people actually order
- A pre-purchase (condition and valuation) survey. The most thorough of the three, ordered by a buyer, paid for by the buyer, and reported to the buyer. It covers condition, safety, and an opinion of market value.
- An insurance survey. Ordered because an underwriter wants to see the boat's condition before writing or renewing a policy. Whether one is required, at what boat age, and how often it must be repeated is set by the insurer, not by any regulation — ask your insurer what they will accept before you book.
- A damage or appraisal survey. Narrow by design: what happened, what it affected, and what it will take to repair, or a value figure for a specific purpose.
The steps below describe a pre-purchase survey, because it is the one that includes everything the others do.
What happens on the day
Identity, first. A competent surveyor starts by finding and recording the Hull Identification Number off the hull itself, plus engine and outboard serial numbers, and compares them to the paperwork. If you have never done this yourself, it is worth knowing where the HIN actually lives on a boat so you can follow along.
The haul-out. The yard lifts the boat in slings or on a travel lift and, in most cases, pressure-washes the bottom. The surveyor then has a short window — often only an hour or two, while the boat hangs — to inspect everything below the waterline: bottom paint condition, blisters, the keel joint or strut and shaft, rudder and bearings, prop, anodes, and every through-hull fitting. Haul-out is arranged and billed separately by the yard, and the buyer usually pays it.
Hull and structure. Sounding a hull with a phenolic hammer is not theatre — a change in tone is how a delaminated or wet-cored area announces itself. The surveyor will also take moisture readings with a meter, work along stringers and bulkheads where they can be reached, and look hard at any area that has been repaired.
Deck and topsides. Core condition underfoot, stanchion and cleat bases, hatches and ports, chainplates, pulpits and rails, and stress cracks radiating from anything highly loaded. On a sailboat, the mast, standing rigging, terminals, and furling gear as far as they can be examined from the deck.
Systems. The engine's installation rather than its internals: mounts, alignment where visible, exhaust, hoses and clamps, raw-water path, belts, fuel tank and lines, and fuel filters. Then batteries and their securing, DC and AC wiring, shore-power protection, bonding, bilge pumps and float switches, seacocks, hoses and clamps below the waterline, the head and holding tank, propane and its shut-off, and CO and smoke alarms.
Safety gear. Life jackets and their sizes and condition, fire extinguishers, visual distress signals, sound signal, navigation lights, and the dates on anything that carries one. Expired gear turns up on a large share of surveys — the dates and what they mean are worth checking before the surveyor does.
The sea trial. Sometimes the same day, sometimes separate. The surveyor watches a cold start, runs the boat up through the RPM range, checks whether she reaches expected wide-open throttle, watches temperature and oil pressure, tests steering and controls under load, and looks at the bilge afterwards. Go with them. A sea trial with the surveyor aboard is where quiet problems tend to speak up.
What a marine survey deliberately does not do
This is the part that surprises first-time buyers, and it is written into the report's own scope section:
- It is non-destructive. The surveyor does not cut into the hull, pull the engine apart, drop the rudder, or remove joinery and tankage to see behind it. Anything inaccessible is reported as inaccessible, not as sound.
- It is not an engine teardown. Most surveyors are not engine mechanics. Compression testing, oil analysis, and internal engine assessment are usually a separate specialist's job, booked separately, and worth every penny on a significant inboard or outboard.
- It is not a warranty or a guarantee. A survey describes what was visible on one day. It does not promise that nothing will break next month.
- It is not a title search. A surveyor records the numbers; they do not tell you whether money is owed against the boat. That is a separate check you make yourself.
Who to hire, and what it costs
In the United States, marine surveying is not a licensed profession — anyone may print the word on a card. Accreditation through SAMS or NAMS is the closest thing to a credential, and many insurers will only accept a report from an accredited surveyor. Outside the US, national bodies and expectations differ, so ask locally.
Two rules that pay for themselves. Hire the surveyor yourself rather than accepting the seller's or the broker's recommendation — you want a report that is written to you and owes nothing to the sale. And ask, before booking, whether the fee is quoted per foot of length, what the sea trial and report cost, and what is excluded. Surveyors commonly price by boat length; the haul-out and any specialist engine work are on top.
Preparing for a survey on your own boat
If it is your boat being surveyed — for insurance, or because you are selling — you can materially change how the day goes:
- Empty lockers, lift floorboards, and clear access to the engine, seacocks, steering gear, and tanks. Anything the surveyor cannot reach becomes a caveat in the report.
- Have the boat clean and dry in the bilge, so a stain means something.
- Charge the batteries and make sure everything that should run, runs.
- Replace expired safety gear beforehand. It is cheap, and it removes a page of findings.
- Put the paperwork in one place: registration or title, past surveys, engine and service invoices, major repair records, and receipts for upgrades.
That last one is the single biggest lever an owner has. A surveyor who is handed a documented history writes a different report from one who is told "it was all done, I just don't have the paperwork" — and so does the buyer's reading of it.
What you get at the end
A written report, and it is a real document: scope and limitations, vessel identity, a description of the boat and its systems, condition findings organised by urgency, moisture readings, an opinion of value where relevant, and the surveyor's recommendations. Read it properly rather than skipping to the number at the end — how to read a survey report covers what each section is actually telling you.
Then keep it. A survey is the most valuable single document a boat accumulates, and it stays valuable to the next owner, the next insurer, and the next surveyor. VesselBook exists for exactly that: surveys and the work done in response to them are filed against the boat's hull number, so the record survives a sale instead of ending up in a folder in someone's garage. You can see what a full history report looks like, and the Trust Score reflects how well documented a hull is — not how good a boat it is.