Buying a Boat That Sat Outside for Years: What Fails, How to Inspect It and What It Really Costs

Ask how long the boat has sat, whether it was covered (and with what), whether the drain plug was in or out, whether it sat level or bow-high, when the engine last ran, and why it stopped being used. "It ran when parked" means nothing about today. Ask for the title and trailer paperwork now; abandoned or long-stored boats often have paperwork problems (see our used boat paperwork guide).

The yard tells a story:

• Uncovered, or a cover that collapsed into a pond: rain filled the cockpit and bilge, often for years.
• Drain plug in, bow up: water collected at the transom, the worst possible spot.
• Sitting in tall grass or under trees: moisture, leaves clogging drains and rodents.
• Tires sunk into the ground or flat: the trailer sat a long time and the tires are done.

Open the drain plug (with permission) and see what comes out. Clear water draining for a long time is a warning that the hull or foam is holding water.

These are the big-money items. BoatUS describes the basics: tap cored areas with a sounding hammer for dull or hollow spots, use a moisture meter if you have one, look for stress cracks, and watch for flex when weight is applied.

• Walk the deck and feel for soft or bouncy spots.
• Tap the transom and deck every few inches; a sharp click is good, a dull thud is suspect.
• On an outboard boat, push and pull hard on the lower unit while a helper watches the transom. BoatUS says you should be able to put your weight on the drive without seeing any flex.
• Look for brown weeping around screws and fittings, cracks around the motor mounting bolts, and fresh caulk over old holes.

On a cored hull or deck, ask whether anyone added through-hulls, transducers or deck hardware below the waterline or on cored areas: BoatUS's refit expert explains that holes drilled through a core without sealing the edges let water creep into it over the years, and a saturated balsa core means cutting off a skin and rebuilding. Also look for stress cracks at the stringers, bulkheads and running strakes; on a planing hull they can be the first sign that the laminate is tired from years of pounding.

See our transom and stringer rot guide for the full check. BoatUS is blunt: when stringers, decks, bulkheads or transoms go soft, the cost to repair almost always eclipses the finished value of the boat.

Many small boats have flotation foam under the floor. Once foam soaks up water, it adds a lot of weight and keeps the surrounding wood wet. Signs:

• The boat sits low or lists on the trailer or in the water
• It feels sluggish and is slow to plane (from the seller's description or sea trial)
• Water keeps seeping from the drain hole long after the bilge is empty
• An inspection plate or hole in the floor shows wet, dark or crumbly foam

Wet foam usually cannot be dried out in place; it has to be cut out and replaced, which normally means removing the deck. See our waterlogged foam guide.

A truck stop or public scale gives a reality check. Weigh the boat on its trailer (fuel tank level noted, gear removed), then subtract the trailer's weight (from its label, or by weighing it empty if you buy it). Compare the result with the builder's published dry weight plus the engine, battery and fuel. Published figures leave out options and rigging, so treat it as a rough check, but a boat that weighs hundreds of pounds more than expected is probably full of water. Some sellers will meet you at a scale; it is worth asking.

Fuel systems suffer badly from sitting:

• Old fuel: gasoline goes stale and ethanol blends can absorb water and separate. Take a sample from the tank or filter (with permission). Water, sludge, varnish or a sour smell means the tank needs draining and cleaning at least.
• Hoses: BoatUS explains that ethanol blends tend to make fuel hoses soft while methanol blends make them brittle, and that a gasoline smell on a rag wiped along the hose means it is breaking down. Flexible fuel hose on a boat must be the Coast Guard-approved marine type, marked on the hose. Hard, cracked or mushy hoses all get replaced.
• Tank: BoatUS notes that aluminum tanks corrode when they stay in contact with water, especially when foam was poured around them, and that replacing a built-in tank can mean cutting the deck. Ask how the tank comes out before you buy.

See our fuel tank inspection and fuel line replacement guides.

Look for corrosion, rodent nests, chewed wires, cracked or missing hoses, and signs of freezing (cracks in the block or manifolds on inboards and sterndrives). Check the oil level and color: milky oil can mean water got in. On inboards and sterndrives, BoatUS calls out the risers, manifolds and raw-water cooling system as places where a failure can let water into the engine. Turn the flywheel by hand (if the seller allows) to see that it is not seized. A compression test (see our compression test guide) tells you far more than a quick start ever will. An oil sample is a cheap second opinion on four-stroke and inboard engines: Blackstone Laboratories says a lab can often spot an early coolant leak, dirt or fuel in the oil before it looks milky, even if the oil was just changed, and that a seller who refuses a sample for no good reason is a red flag (see our oil sample analysis guide). On an engine that sat for years, the oil is old, so judge the results with your mechanic.

Do not assume it will run after a "quick tune-up." Before any start after years of sitting, the fuel system, cooling pump impeller, oil and battery usually all need attention. Plan for that cost even if the engine turns out to be good.

If the seller says the engine was recently put back in running order and offers a water test, ask them not to run it before you arrive, and be there for the first start of the day. A warm engine can hide hard starting, a sticky choke or smoke that shows only when cold. The run itself must happen in the water, or for an outboard on external flush muffs or in a test tank, never dry; inboards and sterndrives only in the water or with cooling water supplied as their manual says.

BoatUS says to plan on replacing basics such as lights, switches and batteries, and warns that old copper wire corrodes (turning green inside the insulation), which raises resistance. Look for:

• Green or black crusty wire ends and terminals
• Household wire, electrical tape, wire nuts and no fuses
• Chewed insulation from rodents
• A battery that is swollen, cracked or dead

The difference between a cleanup and a full rewire is big money; price it honestly.

BoatUS lists failed through-hulls and hoses among the top causes of sunken boats. Check that seacocks open and close (they can seize when unused for years), that plastic through-hull fittings are not brittle from sun, and that hoses are not stiff, cracked or soft. Plan on replacing old bilge and raw-water pumps. Turn the wheel lock to lock: it should be smooth, with no binding, play, leaks or corroded linkages. Old mechanical steering cables often seize after sitting.

BoatUS notes most oxidized gelcoat can be compounded or wet-sanded back to a shine, and two-part paints are an option if UV damage is too deep. Upholstery and canvas can be re-made, but often at significant cost. Press on seats: if the vinyl is cracked and the foam is soaked, the seat bases (often wood) may be rotted too. Check for mold, mildew smell and rodent damage inside lockers and under cushions.

A trailer that sat for years is rarely road-ready. BoatUS suggests checking tires for rot; corrosion on the frame, axles and springs; winches and jacks for sound operation; and whether brakes, if fitted, work. Expect to need tires (check the date code), bearings and lights before towing any distance.

Discover Boating puts typical surveys at about $15 to $25 per foot, and BoatUS cites around $500 per engine for a mechanical survey by a technician who knows that brand. On a cheap small boat, your own careful inspection plus a mechanic's compression test may be enough. On anything bigger, financed or insured, hire a SAMS or NAMS surveyor. BoatUS notes you probably will not be able to finance or insure a larger boat without a survey, and that a surveyor may stop early and let you walk away if a deal-breaker such as structural rot turns up.

Following BoatUS's advice, list every item that needs attention, get a price for each, and add at least 15% for surprises. Get a repower quote even if you hope to keep the old engine; BoatUS recommends it because the only guarantee with an old engine is that it runs today. Include:

• Structure (transom, stringers, deck, foam) if any
• Fuel system: tank cleaning or replacement, hoses, filters
• Engine: service, impeller, carburetor or injector work, or repower
• Electrical: batteries, wiring, switches, lights
• Plumbing, pumps and steering
• Upholstery, canvas and cosmetic work
• Trailer: tires, bearings, lights, winch strap
• Safety gear, registration and taxes

Then compare the total with the price of a turnkey boat of the same size. BoatUS points out that the project often ends up close to the cost of a boat you could use tomorrow. Also be honest about your time, skills and workspace: BoatUS reminds buyers that a yard project may need family approval or even a permit, and some marinas do not allow DIY work.