Boat Detailing Guide: Compare
Buying a Used Boat: A Cosmetic Inspection Checklist
Most used boats are bought on looks first. That is not a bad thing, as long as you know which looks matter. Chalky gelcoat and dirty seats often clean up well and can be a bargaining point. Spider cracks near a cleat, a deck that flexes underfoot or seats that crack when you press them are a different story.
This checklist is for your first walk-around, before you pay for a survey. It covers what to bring, what to look at on the hull, deck, interior and hardware, how to tell cosmetic issues from deeper ones, and where a marine surveyor takes over.
The short answer
On a used boat, check the HIN and title first, then the gelcoat (chalking, fading, repairs, cracks and blisters), the deck and transom for soft spots and flex, the vinyl for cracks and pink stains, carpet and cabin for mildew and smell, and the stainless, glass and canvas. Oxidation and dirt can usually be detailed out; cracks, soft spots, leaks and rotted upholstery cannot. Make any offer subject to a professional survey.
Key points
- Dull, chalky gelcoat is usually restorable; cracks, soft spots and delamination are not cosmetic.
- BoatUS suggests rating each area 1 to 5 and to keep shopping if more than 10 areas score 2 or under.
- Sit on the seats and press the cushions: cracking vinyl and wet foam mean replacement, not cleaning.
- A musty smell points to mildew and often to a leak somewhere.
- BoatUS is clear its checklist is not a substitute for a competent marine surveyor and engine mechanic.
Bring
What to Bring to the Viewing
- A bright flashlight for compartments, the bilge and under the helm.
- A clean white microfiber towel to wipe the gelcoat and test for chalk.
- Your phone for photos of every area, the HIN and any flaws.
- Soft-soled shoes, so you can walk the deck without marking it.
- A printed checklist (BoatUS publishes a free boat evaluation checklist) and a pen.
- Daylight. Viewing a boat at dusk or under a dark boathouse hides fading, repairs and stains.
Paperwork
Start With the HIN and the Title
Federal rules require a 12-character hull identification number, usually on the starboard side of the transom within two inches of the top, with a duplicate in a hidden spot inside the boat. Characters nine and ten give the month (A is January) and last digit of the year of manufacture or certification, and the last two digits give the model year. The HIN must be affixed so that removal or alteration would be obvious, so a scarred, ground-off or mismatched HIN is a reason to stop.
In South Carolina, SCDNR requires titles for motorized boats and outboard motors of five horsepower and up, and says to make sure the boat and motor are titled to the person you are buying from. Match the HIN on the boat to the title before you fall in love with the paint.
Hull and deck
Gelcoat: Cosmetic or Deeper?
Do the towel test
Wipe a hull side with the white towel. Color on the towel means oxidation. BoatUS says time and sun erode gelcoat until it is dull and chalky, but the gloss usually can be restored, so heavy chalk is a cleaning and correction cost, not a deal breaker by itself.
Look for fading and patches
Sight down the hull at a low angle. Colored stripes and hulls fade faster than white. Patches of different color or texture usually mean past repairs; ask about them.
Check for peeling restorer
Flaking or yellowed patches with a plastic-looking film can be a gelcoat restorer coating. BoatUS notes these can wear, flake and discolor and need a special stripper before the gelcoat can be corrected.
Hunt for cracks
Look closely around cleats, rails, hinges, the windshield base, the transom corners and anywhere the boat flexes. BoatUS notes some gelcoat cracking is cosmetic, but extensive or long-unattended cracks can let moisture into the deck or hull.
Walk and press
Walk the deck and cockpit floor and feel for flex or spongy spots. BoatUS says that when stringers, decks, bulkheads or transoms go soft, the repair cost almost always exceeds the finished value of the boat. On an outboard boat, BoatUS says the transom shouldn't flex when you put your weight on the drive.
Look below the waterline
If the boat is on a trailer, check the bottom for blisters, deep gouges and keel damage. Note bottom paint, which affects later care.
Interior
Seats, Carpet, Cabin and Smell
- Sit on every seat and press each cushion. Vinyl that cracks, feels hard or has split seams needs repair or replacement; cleaning will not fix it.
- Squeeze cushions near the seams and on the underside. Water that seeps out or a sour smell means wet foam, which usually means replacement.
- Look for pink or orange staining under the vinyl surface. Some stains lighten with proper cleaning; deep pink staining often doesn't fully come out.
- Lift snap-in carpet and check the backing and the floor under it. Black spots, rot or a musty smell mean the carpet is done and the floor should be checked.
- Open the cuddy or console: look at the headliner for sagging and the liner for water lines under portlights and hatches. BoatUS lists portlights and deck hardware as the top leak sources.
- Trust your nose. A musty cabin or locker is mildew, and mildew usually means water got in somewhere.
- Open every compartment and the bilge access with the flashlight. Rust, standing water, oil and debris all tell you about care.
Hardware
Stainless, Glass, Canvas and Non-Skid
- Stainless and chromeMostly cosmetic
- Brown surface rust on stainless usually polishes off. Pitted or flaking chrome stays pitted. Loose rails and cleats with cracks around them are a structural and leak concern.
- Windshield and clear vinylCheck clarity
- Light film cleans off. Deep scratches, crazing in acrylic and yellowed, cloudy or brittle clear vinyl need replacement.
- Canvas and biminiCheck seams
- Mildew spots can often be cleaned; torn seams, worn-through fabric and seized frames are repair or replacement items.
- Non-skidClean, not polish
- Dirty non-skid scrubs up. Worn-smooth non-skid or cracks in the texture are not a detailing fix.
- WaterlineUsually cleanable
- A brown lake line is common and usually comes off with the right cleaners. Waterline stains
Scoring
Turn the Walk-Around Into a Decision
The BoatUS evaluation checklist suggests rating each area from 1 (poor) to 5 (excellent), making a copy for each boat you look at, and continuing to shop if a boat has more than 10 scores of 2 or under. It is a quick way to compare boats you saw on different weekends without relying on memory.
Then split your notes into two lists. Cosmetic items a detail can address: oxidation, waterline, dirty vinyl, stained carpet that is otherwise sound, streaked stainless, filmy glass. Everything else: cracks, soft spots, leaks, wet foam, rotted carpet backing, damaged clear vinyl, mechanical questions. The first list is a negotiating point. The second list needs a professional opinion and possibly a walk away.
Survey
Where the Surveyor Takes Over
BoatUS is explicit that its checklist is not a substitute for a competent marine surveyor and a marine engine mechanic. A surveyor works for you, not the seller. BoatUS says the two main associations are SAMS and NAMS, and some insurers accept only one; both have directories.
A typical prepurchase survey includes an in-water inspection, a short haul-out to see below the waterline, and a trial run. Surveyors check first for water intrusion, rot in bulkheads or stringers, hull-to-deck joint separation and delamination, and out of the water they look for blisters. Most general surveyors are not engine specialists, so BoatUS suggests a separate mechanical survey on boats where the engines are a big part of the value. Even new boats have findings; a survey with none, BoatUS says, probably wasn't thorough.
| What you see | Likely cosmetic? | Next step |
|---|---|---|
| Chalk on the towel, dull hull | Yes | Price in correction and protection |
| Brown waterline, rust streaks | Yes | Detail; usually cleanable |
| Patches of different color | Maybe | Ask about past repairs; surveyor |
| Cracks near hardware or corners | Maybe not | Surveyor; possible moisture entry |
| Spongy deck, flexing transom | No | Surveyor; often walk away |
| Blisters below the waterline | No | Surveyor |
| Dirty but supple vinyl | Yes | Proper vinyl cleaning |
| Cracked vinyl, wet foam | No | Price in upholstery work |
| Musty cabin, water lines | No | Find the leak; surveyor |
| Altered or missing HIN | No | Stop until explained |
Bought It? Get It Cleaned Up
Once the boat is yours, send us the make, model and length, its condition and where it will be kept. We'll reply with a quote for the exterior, interior or both.
Common questions
Is oxidized gelcoat a reason not to buy a boat?
Not on its own. BoatUS notes the gloss on dull, chalky gelcoat usually can be restored with cleaning, compounding, polishing and waxing. Treat heavy oxidation as a cost to factor into your offer. Be more cautious if the gelcoat looks thin or see-through, has many cracks, or has been coated with a restorer that is now peeling.
How can I tell if a boat has soft spots?
Walk the deck, cockpit floor and swim platform slowly and feel for flex or a spongy give, and press on the transom and around hardware. BoatUS describes tapping cored areas for dull or hollow sounds and checking that an outboard's transom doesn't flex under your weight. A surveyor's moisture meter and sounding hammer confirm it. Soft structure is expensive to fix.
Do I really need a survey on a small used boat?
BoatUS acknowledges a survey may not make sense on very small boats like skiffs, but warns that skipping one can cost much more later, and that many lenders and insurers require a survey. On a fiberglass boat with cored decks or an inboard engine, a survey is cheap protection. At minimum, have a mechanic check the engine.
Can pink stains on used boat seats be removed?
Sometimes they lighten, but they often don't fully disappear. Pink staining usually sits below the vinyl surface rather than on it, so surface cleaning has limited reach. Try a marine vinyl cleaner and a soft brush; avoid bleach, which harms the vinyl and stitching. Price in the chance that badly stained seats will stay stained or need new covers.
Sources
- Boat Buyer's Guide: Boat Evaluation Checklist, BoatUS (https://www.boatus.com/app/views/201805/checklist.asp), accessed October 2026
- The Boat Survey, BoatUS Magazine, January 2026 (https://www.boatus.com/expert-advice/expert-advice-archive/2026/january/the-boat-survey), accessed October 2026
- The Value Proposition (evaluating a project boat), BoatUS Magazine, June 2026 (https://www.boatus.com/expert-advice/expert-advice-archive/2026/june/value-proposition), accessed October 2026
- What a Surveyor Should Look For, BoatUS (https://www.boatus.com/expert-advice/expert-advice-archive/2014/january/what-a-surveyor-should-look-for), accessed October 2026
- Restoring The Shine To Fiberglass, BoatUS (https://www.boatus.com/expert-advice/expert-advice-archive/2019/february/restoring-the-shine-to-fiberglass), accessed October 2026
- Preventing Mold And Mildew, Charles Fort, BoatUS Magazine (https://www.boatus.com/expert-advice/expert-advice-archive/2016/january/preventing-mold-and-mildew), accessed October 2026
- 33 CFR 181.25 and 181.29, Hull identification number format and display, Electronic Code of Federal Regulations (https://www.ecfr.gov/current/title-33/chapter-I/subchapter-S/part-181), accessed October 2026
- Title and Register a Watercraft or Outboard Motor in SC, South Carolina Department of Natural Resources (https://dnr.sc.gov/boating/Titling_and_Registration/index.html), accessed October 2026
Boat detailing is quoted per boat, so this guide does not list boat prices. Product directions and warranty terms come from the manufacturer: follow your boat builder’s care instructions where they differ from general advice here.