Used sailboat inspection checklist: before you travel, at the viewing, and what only a surveyor can tell you
By Itzhak Fuhrman·Built and maintains Knotworth's cost model·Updated 9 September 2026
Most inspection checklists are written as if you are already standing on the boat. That is the wrong starting point, because by the time you are standing on the boat you have spent money getting there.
The expensive mistake in used-boat buying is not missing a soft spot on deck. It is flying to see a boat that a ten-minute email exchange would have ruled out.
So this checklist is in three stages, and the first one costs nothing. Each stage ends with the decision it lets you make.
The whole thing is also available as a free printable PDF, no sign-up, at the end of this page.
What can you check before you travel?
More than most buyers think. From the listing, the hull number and a short list of questions to the seller, you can establish the rig age, the engine's identity and service history, whether she has been aground, which model-specific faults apply, and whether the seller's silences are the expensive kind. Cost: nothing. Decision: whether to book the flight.
This is the stage the rest of the internet skips, and it is where the money is.
| Check | How, from your desk | What a good answer looks like |
|---|---|---|
| Which boat is she, exactly | Hull identification number (HIN) from the listing or the seller. Year, builder, hull number | Matches the listing. On some models the hull number alone changes the price: Valiant 40s numbered 120 to 249 carry a documented blister resin, and no listing states the hull number unprompted |
| The model's documented faults | Read the model's buyer guide before you read the listing. Every builder has a known list | You arrive knowing what to ask. See the sailboat guides for Catalina, Westsail, Island Packet, Cape Dory, Beneteau, Hunter and Tartan |
| Standing rigging age | Ask: "When was the standing rigging last replaced, by whom, and is there an invoice?" | A year, a rigger's name and a receipt. Wire rigging has a working life of roughly ten to fifteen years, and insurers increasingly ask. "Looks fine" is not an answer |
| Engine identity and hours | Ask for the make, model, hour-meter reading and the service log | A named engine, a number, and a log with dates. See the engine hours section below for how to read the number |
| Grounding history | Ask: "Has she ever been aground, and what was done afterwards?" | Either "no", or a yard invoice describing the repair. On a Beneteau this matters more than on almost any other brand, because the keel bolts to a grid whose bond a survey cannot see |
| Keel type and draft | From the listing. Fin, wing, shoal, full, encapsulated | Know what a grounding would have hit first. On the shoal-draft Catalina 36 that is the rudder |
| Through-hulls | Ask: "Are the through-hulls proper seacocks or original gate valves?" | Seacocks. Gate valves on 1970s and 1980s production boats are a known replacement item at several hundred dollars each installed |
| Tanks | Ask what the fuel and water tanks are made of and how they are mounted | Any answer that shows the seller knows. On some models the mounting is the fault: Cape Dory aluminium tanks sat on plywood with wooden cleats and corroded from underneath |
| Chainplates | Ask for a photograph of each chainplate where it passes through the deck, and of the bulkhead below | No staining, no crazing, and if the model is known for embedded or failing chainplates, evidence they have been replaced. Applies to Island Packet 1980s and 1990s hulls and the Catalina 27 among others |
| Previous survey | Ask: "Is there a survey report from your purchase, and may I see it?" | A dated report. Its findings list is your viewing checklist |
| Berth and haul-out length | From the specs. Overall length including bowsprit and boomkin, not length on deck | You pay for the longer number. A Westsail 32 is 32 feet on deck and 40 feet on the marina invoice |
| Photographs of the unglamorous | Ask for photos of the bilge, the engine compartment, the chainplate bases and the keel joint | A seller who sends them quickly has nothing to hide. One who sends more cockpit cushions instead has told you something |
What silence means. A listing that does not mention the rigging age has told you nothing about the rigging. Treat every omission as a question, never as a quiet assumption that the work was done.
What this stage decides. Whether the boat is worth a flight and a hotel. A boat that cannot answer the rigging, engine and grounding questions with documents is not disqualified, but she is priced as a boat carrying that uncertainty, and you should decide whether to travel on that basis.
The free pre-check does this stage automatically: paste a listing URL and it pulls the specification, runs the design numbers and flags which of these questions the advertisement is silent on.
What to check at the viewing
Everything your own eyes, hands and nose can reach without tools or a haul-out. Walk the deck listening for the dull thud of wet core, look under every fitting, open every locker, and start the engine cold. Cost: your travel. Decision: whether to commission a survey.
Bring a torch, a small screwdriver for tapping, a notebook and the model's fault list. Wear clothes you can crawl in. Allow two hours minimum and do not let the seller set the pace.
| Where | What to do | What you are looking for |
|---|---|---|
| Deck | Walk every square foot, pressing with your heel. Tap around each fitting with a screwdriver handle | Soft spots, a dull sound instead of a sharp one, spider crazing in the gelcoat around stanchions, cleats and the mast base. Cored decks rot from the fittings inward |
| Chainplates, on deck | Look at each one where it meets the deck | Cracked or lifting sealant, rust weeping, crazing in the surrounding gelcoat |
| Chainplates, below | Open the lockers and look at the bulkhead or knee each chainplate bolts to | Brown staining, softness when pressed, delaminated tabbing. This is how rigs are lost |
| Standing rigging | Run a rag along each wire near the swages. Look at every terminal | Broken strands catch the rag ("meat hooks"). Cracks in swage fittings. Rust bleeding from inside a terminal |
| Mast base and step | Look at where the mast meets the deck and, below, where the load lands | Compression of the deck, a cracked or crushed step, a wooden compression post that is soft |
| Hull, outside | Sight along the topsides in low light. Look at the keel joint | Fairness. Repairs show as slight waviness. A visible seam or weeping at the keel-to-hull joint |
| Bilge | Lift every sole board. Smell first, then look | Standing water, oil, a musty smell, rust around the keel bolts, staining that shows how high water has stood |
| Keel bolts | Look at the nuts and the surrounding glass | Rust weeping, cracked glass around the bolt heads, evidence of previous grinding or filling |
| Through-hulls | Turn every one | Seacocks turn freely and shut. Gate valves seize, and you cannot tell open from closed by looking |
| Rudder and steering | Grab the rudder from the dinghy or the dock and push. Turn the wheel or tiller lock to lock | Play in the bearings, clunking, stiffness. Delamination at the rudder's leading edge |
| Engine, cold | Insist she has not been run that morning. Start her yourself | White or blue smoke that does not clear, hard starting, knocking. Then look for oil in the bilge under the engine, coolant weeps, and a stern gland that drips more than once every few seconds |
| Engine compartment | Look, touch, smell | Rust on the block, salt trails, chafed hoses, a fuel smell, a cleaner engine than the rest of the boat (freshly painted engines are a question, not an answer) |
| Tanks | Find them. Look at how they are mounted | Aluminium on wood, steel with rust, plastic that has gone cloudy. Ask when they were last opened |
| Electrical | Open the panel. Follow some wiring | Marine tinned cable, labelled runs, proper terminals. Household wire and twisted joints mean an amateur has been in here, and probably elsewhere |
| Sails | Unroll them, all of them, on the dock if you have to | Crinkled or soft cloth, thinning at the leech, stitching failing, sun damage on the furled edge |
| Ports, hatches, windows | Look at the headliner and cushions beneath each one | Water staining, rebedding attempts, cloudy acrylic. This is where most interior water comes from |
| Interior joinery and tabbing | Press on bulkheads. Look where furniture meets the hull | Movement, cracked tabbing, filler. On kit-built boats like half the Westsail 32 fleet, this is the whole question |
| Ground tackle and deck gear | Look at the anchor, chain and windlass | Rusted chain, a windlass that does not turn, an anchor too small for the boat |
Checks specific to the model. Bring the "what to check before you buy one" list from the boat's guide. On a Catalina 22 that means the swing keel pivot and cable. On a Cape Dory 28 it means the fuel tank mounting and crazing at the chainplates. Generic checklists miss exactly the things that are specific.
What this stage decides. Whether to spend real money on a professional survey. If the deck is soft, the bilge is rusty and the engine smokes, you do not need a surveyor to tell you to walk away. If she passes your hands, she has earned the survey.
What can only a surveyor tell you?
The things that need instruments, a haul-out or a sea trial. Moisture readings through the hull and deck, the keel joint and rudder bearings out of the water, the engine under load, and a written report your insurer will accept. Cost: several hundred to a few thousand dollars depending on length and haul-out. Decision: buy, renegotiate, or walk.
A surveyor is not a repeat of stage two with more authority. They do things you cannot.
- Moisture meter and percussion across the whole hull and deck, mapping wet core you could only guess at with your heel.
- Haul-out inspection: the keel joint under load, the rudder bearings, the propeller and shaft, the through-hulls from outside, blistering below the waterline.
- Sea trial: the engine at cruising revs for long enough to show its temperature and its smoke, the rig under load, the steering under way.
- Rig inspection aloft, or a recommendation to have a rigger do it.
- Engine oil analysis, if you ask for it, which reads wear metals the hour meter cannot.
- A written report that an insurer accepts and a seller has to answer.
How much does a marine survey typically cost? Enough that you want stage one and two to have happened first. The survey cost guide breaks the day down line by line, including the haul-out and yard fees that the surveyor's rate does not mention, and lands at well over a thousand dollars on a mid-size boat once everything is counted.
Choose the surveyor, not the seller's surveyor. Accredited through SAMS or NAMS, working for you, paid by you. A survey commissioned by the seller is marketing.
What this stage decides. The price. A survey that finds nothing confirms the asking price. A survey that finds a wet deck and a tired rig gives you a written, costed list to negotiate from. The true-cost guide shows how to turn that list into a number.
How many engine hours is too many?
Fewer than you would think, and the number matters less than the log. Owner consensus across the sailing forums puts the expected life of a small marine diesel at around 8,000 hours, with 10,000 achievable, and heavy slow-revving engines outlasting light high-revving ones. A well-documented 4,000-hour engine is a better buy than an undocumented 1,500-hour one.
This is one of the questions Google shows people asking most about used boats, and the honest answer has three parts.
Hours are a weak signal on their own. Owner reports on Sailboat Owners Forums and elsewhere describe seventeen-year-old diesels past 10,000 hours running clean, and the same engine at half the hours on another boat burning oil. The difference was maintenance and use, not the meter.
Low hours can be the worse sign. Marine diesels corrode when they sit. An engine that has done 300 hours in fifteen years has spent most of its life not running, which is how injectors gum, exhaust elbows rot and raw-water passages block. Manufacturers specify calendar-based service intervals for exactly this reason.
Engine type sets the ceiling. Older, heavier, slower-running engines such as the Perkins 4108 and the Westerbekes are commonly reported lasting twenty-five to thirty years. Lighter, higher-revving modern units are more often quoted at ten to fifteen. On a 1980s production boat the engine is a large part of the price whichever it is, because a repower is a five-figure job.
What to ask for instead of the number. The service log with dates. Oil-change intervals. When the heat exchanger was last cleaned and the exhaust elbow last replaced. Whether the raw-water impeller is changed annually. An engine with those answers is a known quantity at any hour count.
Sources: owner discussion on Sailboat Owners Forums, YBW and Latitude 38. These are owner reports, not manufacturer figures, and they are labelled as such.
The printable checklist
All three stages on two pages, with tick boxes, free, no sign-up. Print it, take it to the viewing, and hand the third page to your surveyor so they know what you have already checked.
It is the same content as this page, laid out to be used on a dock rather than read on a screen. If you find something missing from it, the address is on the about page and corrections that hold up get applied.
How Knotworth does stage one for you
The pre-check is stage one, automated. Paste a listing URL and it reads the specification, runs the design numbers, and lists which of the questions above the advertisement does not answer. Free, no card, and the output is the email you would have written to the seller.
Stage one is the stage that saves the most money and the stage almost nobody does properly, because it is tedious. Reading a listing against a model's fault list, checking the rig age against the year, noticing that the engine is not named.
That is a job for software. The free pre-check does it in a minute, and the sample report shows what the paid version adds when you decide the boat is worth the flight.
Then you go and do stage two with your own hands, which no software can.
Paste the URL. The free pre-check reads the boat's specs, runs her design numbers, and lists what the ad leaves unanswered. No card, no sign-up to see the result.
FAQ
What should I check when buying a used sailboat?+
Three things in order. Before travelling: the rig age, the engine's identity and service log, any grounding history, the model's documented faults and whether the seller can answer with documents. At the viewing: the deck for soft spots, the chainplates above and below, the bilge and keel bolts, the through-hulls, the rudder for play, and the engine started cold. Then a surveyor for the moisture readings, the haul-out and the sea trial.
What can I inspect myself without a surveyor?+
Anything your eyes, hands and nose reach without instruments or a haul-out: deck softness by tapping and pressing, gelcoat crazing at fittings, chainplate staining below deck, bilge condition, rust at the keel bolts, rudder play, seacock operation, engine cold start and smoke, wiring quality, and the sails unrolled. That is enough to decide whether the boat deserves a paid survey.
How much does a marine survey typically cost?+
Several hundred to a few thousand dollars depending on the boat's length and whether a haul-out is needed, and on a mid-size boat the full day comes to well over a thousand once yard fees are included. The survey cost guide on this site breaks it down line by line with published rate cards.
How many hours is too many on a used sailboat engine?+
Owner consensus puts the expected life of a small marine diesel around 8,000 hours, with 10,000 achievable on heavy slow-revving engines. The service log matters more than the meter: a documented 4,000-hour engine is a safer buy than an undocumented 1,500-hour one, and very low hours can mean an engine that has corroded from sitting.
Should I get a survey on a cheap boat?+
Do stages one and two first, and let them decide. On a $5,000 boat a survey can be a quarter of the price, which is an argument for asking the free questions and doing the viewing thoroughly, not an argument for skipping the survey if she passes them and you are still uncertain.
Can I use the seller's survey?+
Read it, because its findings list is useful, but do not rely on it. A survey is commissioned by and works for whoever pays for it. Yours should be by a SAMS or NAMS accredited surveyor you chose.
Is the checklist free?+
Yes, the page and the PDF, with no sign-up. The free pre-check is also free with no card required. Knotworth charges once per boat only when you choose to unlock a full report.