How to Inspect a Used Boat Before You Buy

On the phone (not only by text or email, which scammers prefer), ask: how many engine hours, what maintenance was done and is there paperwork, where the boat was stored, fresh or salt water, why they are selling, and whether the title is in their name with no loan on it. Look up the make and model for known problems and check the US Coast Guard recall search, which you can search by company name or by the Manufacturer Identification Code (the first three characters of the HIN). BoatUS explains that a Coast Guard safety recall applies to boats and equipment less than 10 years old, and the maker must fix it at no charge even if the defect is found years later; haulout and travel costs are usually yours. Never buy a boat you have not seen in person or had someone you trust look over.

Find the 12-character Hull Identification Number (HIN) on the starboard (right) side of the transom, near the top. It must match the title or registration exactly. Many states title boats, but the rules vary by state, so check with yours; some also title the trailer separately.

Walk away if the HIN is missing, ground off, painted over or looks altered: it is illegal to alter or remove a HIN. Boats built after August 1, 1984 also have a second, hidden HIN somewhere inside the hull. Ask about liens, and if the boat has no title, ask for the seller's own bill of sale as proof of ownership. Larger boats are often Coast Guard documented instead of (or as well as) state titled. For those, you can request an Abstract of Title from the Coast Guard's National Vessel Documentation Center; it lists the mortgages and lien notices recorded while the boat was documented. It is not a complete history (a boat may have spent years state-registered, and recording most liens is optional), so lenders and buyers often also use a documentation service or a title search. Write down the engine serial numbers too; you will need them for manuals, parts and records.

Look along the hull in good light, ideally out of the water. Note:

• Cracks, especially star-shaped or long straight ones near the transom, chines, hull-to-deck joint or where hardware is mounted
• Blisters below the waterline
• Patches that do not match the gelcoat color (past repairs: ask what happened)
• Damage to the keel and bow from beaching or trailering
• A gap or separation along the hull-to-deck joint

Some gelcoat crazing is cosmetic, but long-ignored cracks can let water into the core.

These are the big-money items. Tap the transom and deck every few inches with a plastic mallet: a sharp click is good; a dull thud can mean a void or wet core. Walk the deck and feel for soft or bouncy spots.

On an outboard boat with the motor tilted down, grab the lower unit and push and pull hard, leaning some body weight into it, while a helper watches the top of the transom and the motor brackets. The transom should not flex. Cracks around the motor mounting bolts, rust or brown stains weeping from screws, and fresh caulk over old holes are warning signs. See the transom and stringer rot guide for a full check. Soft structure usually costs more to fix than the boat is worth.

Use the flashlight and mirror. Look for oil, fuel or a fuel smell, standing water, sawdust-like debris (rotting wood), and a bilge pump that works. An older boat that sits low, lists or feels sluggish may have waterlogged flotation foam under the floor, which usually travels with rotten stringers (see our waterlogged foam guide). Check hoses for cracks and double clamps, through-hull fittings and seacocks that open and close, and wiring that is neat, protected and fused rather than a tangle of household wire and tape. Ask permission to take a small fuel sample: water or gel in the jar means the tank needs attention.

Ask what the fuel tank is made of and how old it is. Mercury warns that some fiberglass tanks built before 1991 may not be compatible with ethanol fuel, and on engines from 1990 or earlier it advises checking every fuel line and fitting for softening, swelling or leaks. Old fuel hoses that feel hard or mushy are a negotiating point, not a detail.

Look for corrosion, salt crust, oil leaks, chafed wires and discolored or blistered paint (a sign of past overheating). Check the oil level and color on four-strokes: milky oil is a serious warning.

Do not trust the hour meter alone. Meters can be replaced or disconnected. Compare the hours with the maintenance records and the general wear on controls, seats and hardware. Many modern engines store their running hours in the engine computer, which a dealer can read with a diagnostic tool.

With the seller's OK, crack the lower drain screw on an outboard or sterndrive gearcase and let a few drops out. Clean, honey-colored gear oil is good. Milky or gray oil means water is getting past the seals. Metal flakes or a lot of fine glitter on the drain magnet point to worn gears. On sterndrives, look at the rubber bellows for cracks and ask when they were last replaced. Check the propeller for dings and the shaft for wrapped fishing line.

A compression test is one of the best checks on an older engine. With the engine warm and the kill switch clip removed, all spark plugs are taken out, a gauge is threaded into each plug hole in turn, and the engine is cranked with the throttle wide open for the same number of turns on every cylinder.

Your service manual gives the expected range, but what matters most is that the cylinders read close to each other. One cylinder much lower than the rest can mean worn rings, a burned piston or a valve problem. If you are not comfortable doing this, a mechanic can do it for a modest fee; our compression test guide walks through it step by step. Low or uneven compression is a strong reason to walk away or renegotiate for a repower.

Turn on and check every system: battery switch, gauges, horn, navigation lights, bilge pump and blower, power trim and tilt, steering from lock to lock (it should be smooth, with no binding or play), and the shift and throttle controls. Electronics should power up. Write down anything that does not work: it is money off the price or a reason to walk.

Have the seller start the engine cold, with cooling water available. It should start without long cranking. A puff of smoke on a 2-stroke is normal; heavy, continuous smoke is not. On outboards, check that the cooling water telltale stream comes out strong within a few seconds. Listen for knocking or rattling.

Any boat worth buying is worth a sea trial; if the seller refuses, walk away. For a trailer boat, meet at the launch ramp so you can also see the trailer in use. Let the seller drive away from the dock and back, then ask to take the helm for a while.

• Let the engine warm up, then run it at wide-open throttle briefly. The RPM should reach the range your engine maker specifies.
• Check how quickly the boat gets on plane, whether the steering pulls, and whether you feel vibration.
• Shifting should be smooth between forward, neutral and reverse.
• Watch the gauges and listen for alarms, then check the bilge again afterward for new water.

Check the tire date codes and sidewalls for cracks, the wheel bearings for noise or heat, the lights, the frame for rust and cracks, the bunks or rollers, the winch strap and the coupler. Make sure the trailer is rated for the weight of the boat, engine and fuel.

A surveyor works for you, not the seller. Look for a member of SAMS (Society of Accredited Marine Surveyors) or NAMS (National Association of Marine Surveyors), and ask your insurer and lender which they accept. Discover Boating puts typical survey prices at about $15 to $25 per foot of boat.

Most surveyors only inspect the engine externally. For a full engine check (compression, oil analysis, diagnostic scan), hire a mechanic who knows that engine brand; BoatUS cited about $500 per engine. Some engine makers also offer factory-backed coverage for used engines: Mercury's Certified Pre-Owned plan, for example, lets an authorized dealer inspect and certify a used Mercury engine that has no remaining warranty and sell a one- or two-year plan. Ask the selling dealer whether the engine qualifies. If the engine is young enough to still have factory warranty, an authorized dealer can check the remaining coverage from the serial number, and Mercury, for example, transfers the remaining warranty to a new owner when you send it a copy of the bill of sale; other brands have their own process, so ask. Attend the survey, ask questions, and make your offer subject to an acceptable survey and sea trial.

Use a written bill of sale or purchase agreement that lists the boat, engine and trailer serial numbers and every item included (electronics, spare prop, safety gear). Your state's boating agency, BoatUS and the Coast Guard offer blank forms. Pay only when you receive a clean, signed title (or proof of ownership), then register the boat in your state and arrange insurance before you launch.