Marine Surveys Explained, What a Surveyor Checks

What a marine survey is, and what it is not

A marine survey is a professional inspection of a vessel's condition, written up in a report that also usually states the surveyor's opinion of fair market value and replacement cost. For a yacht buyer, the pre-purchase survey is the most important few thousand dollars in the deal. Lenders and insurers usually require one, and the findings are the normal basis for renegotiating price.

It is important to understand the limits. A survey is non-destructive. The surveyor will not cut holes in the deck, pull engines apart, or remove fixed panels and headliners without the owner's permission. Areas that cannot be reached are noted as not inspected. A good surveyor will tell you what they could not see as clearly as what they found, and will recommend further investigation when the evidence warrants it.

The US Coast Guard does not certify or license recreational marine surveyors, so the profession is largely self-regulated through professional associations. That makes choosing the right person your job.

The main types of marine survey

Different surveys answer different questions. Make sure you order the one that fits your purpose.

How to choose the right surveyor

In the US, the most commonly cited credentials for yacht surveyors are the AMS designation from the Society of Accredited Marine Surveyors (SAMS) and the NAMS-CMS designation from the National Association of Marine Surveyors, which certifies members in categories including yachts and small craft. The International Institute of Marine Surveying (IIMS) is another recognized body. Many lenders and insurers ask for a surveyor with one of these credentials.

Credentials are a floor, not a ceiling. A surveyor who mainly inspects center consoles may be the wrong person for a 1985 cutter-rigged cruiser or a twin-engine catamaran. Ask these questions before you hire:

• How many boats of this type and size have you surveyed in the past two years?
• What does your inspection include, and what will you exclude?
• Do you use a moisture meter, and how do you confirm readings? Do you use thermal imaging or ultrasonic thickness testing where relevant?
• Who do you recommend for the engine and rigging surveys?
• Can I attend, and how quickly will the written report arrive?
• Do you have any relationship with the seller or the listing broker?

What a survey costs

Pricing varies by region, boat type and complexity, so treat these as editorial estimates. Multihulls, boats with complex systems and older boats needing more time can cost more. Remember that the buyer typically pays for all inspections, the haul-out and sea trial fuel, whether or not the deal closes.

Out of the water, what the surveyor looks for below

The haul-out is where many deal-breaking problems appear. With the boat in the slings or on blocks, the surveyor examines the bottom while it is still wet, which is when moisture readings are most informative.

Expect the surveyor to sound the hull with a phenolic hammer, listening for the dull note of voids or delamination, and to take moisture meter readings across the bottom and topsides. Readings are relative and need interpretation, so elevated numbers lead to further investigation rather than an automatic verdict. On metal hulls, ultrasonic thickness gauging measures plate loss from corrosion.

• Blisters, their size and density, and whether they are in the gelcoat or deeper in the laminate.
• The keel-to-hull joint on fin-keel sailboats, looking for cracks or a gap that suggests grounding or bolt problems.
• Rudder bearings, rudder play and moisture inside the rudder.
• Propellers, shafts, cutlass bearings, struts and saildrive seals.
• Through-hull fittings and seacocks, plus the condition of anodes and any signs of stray-current corrosion.
• Trim tabs, thrusters, stabilizer fins and transducers, and the hull around them.

Deck, structure and the leaks you cannot see

Cored decks and hulls are light and stiff, but water entering through poorly bedded hardware can saturate the core, leading to soft spots and, in freezing climates, delamination. Surveyors sound the deck around stanchions, cleats, winches, chainplates, hatches and windlass, and take moisture readings in suspect areas.

Inside, the surveyor checks bulkhead and stringer tabbing, the hull-to-deck joint, chainplate attachments, mast step and engine beds. Water staining on cabinetry or headliners, rust trails and compression at the mast step all point to leaks that may have been going on for years. On power boats, transom and stringer condition get extra attention because they carry the loads from engines, drives or outboards.

Systems and safety, measured against standards

Most US surveyors evaluate systems against the voluntary standards published by the American Boat and Yacht Council (ABYC), along with the mandatory USCG requirements for recreational vessels. A finding that a system does not meet a current ABYC standard does not always mean it is dangerous, especially on older boats built before that standard existed, but safety-related deviations are flagged.

Areas usually examined include AC and DC electrical systems (wire sizing, overcurrent protection, battery installation, shore power and galvanic isolation), fuel systems and fuel lines, LPG installation and solenoid, exhaust systems and carbon monoxide detection, bilge pumps and high-water alarms, plumbing, heads and holding tanks, steering, navigation lights, and electronics. Safety gear is checked against federal carriage requirements: life jackets, fire extinguishers, visual distress signals and sound-producing devices, plus ventilation on gasoline boats.

Engines and rigging, the specialist inspections

A general surveyor will note the visible condition of engines, but most do not perform detailed mechanical evaluations. On any diesel yacht, and certainly on twin-engine motor yachts where engines can represent a large share of the boat's value, hire a marine engine surveyor. They typically review service records and engine hours, check for leaks and corrosion, take oil samples from engines, gears and generator for laboratory analysis, scan electronic engines for fault codes, and run each engine under load during the sea trial while recording temperatures, pressures, RPM and smoke. Compression testing or a borescope inspection may be recommended when results suggest a problem.

On sailboats, the mast and rig are the largest single item a general survey may not fully cover from deck level. A rigger who goes aloft can inspect swage fittings for cracks, check spreader roots, sheaves, tangs and the masthead, and assess roller furlers. Many insurers have rules about the age of standing rigging, so ask what yours requires.

The sea trial, and how to run it

The sea trial puts the whole boat under real loads. On power boats, the engines should warm up, run at cruise and briefly at wide open throttle to confirm they reach rated RPM, then come back to idle while the surveyor checks for vibration, overheating and smoke. Steering, trim tabs, thrusters, stabilizers, autopilot and electronics should all be tested. On sailboats, hoist and reef every sail, tack and gybe, and motor at cruise RPM to check engine temperature and shaft alignment.

Sea trials are usually limited in time, so agree a plan beforehand. Bring a notebook or record observations on your phone, and ask the surveyor to explain anything unusual as it happens.

Reading the report and using it to negotiate

A survey report lists findings and recommendations, often ranked by priority. Some surveyors use categories such as items affecting safety, items to address before launch or within a set period, and general maintenance notes. The report also includes a valuation section stating fair market value and replacement cost based on comparable sales.

Sort the findings into three groups. Safety issues should be fixed before you use the boat, and it is fair to ask the seller to pay for them or reduce the price. Value-changing defects, such as wet core, failing engines or structural repairs, justify a price renegotiation or a decision to walk away. Normal wear consistent with the boat's age was presumably reflected in your offer and is a weak basis for negotiation.

Get repair estimates from yards before you negotiate, not after. A specific quote carries more weight than a guess, and it tells you whether the problem is a weekend fix or a season in the yard.

Models mentioned in this guide

Catalina 30

Cruising Sailboats, 30 ft

Used $8K to $58K

Cape Dory 36

Bluewater Sailboats, 36 ft

Used $35K to $95K

Lagoon 450

Sailing Catamarans, 46 ft

Used $250K to $580K

Sea Ray 480 Sedan Bridge

Motor Yachts, 51 ft

Used $200K to $350K

Hatteras 70 Motor Yacht

Motor Yachts, 75 ft

Used $350K to $4M

Grand Banks 42 Classic

Trawlers & Explorer Yachts, 43 ft

Used $75K to $360K