What Marine Surveyors Look For

Marine surveys have gotten complicated with all the horror stories flying around. As someone who’s been through the survey process more than once, I learned everything there is to know about what surveyors actually check. Today, I will share it all with you.

Quick Answer: Marine surveyors dig into hull structure, deck and superstructure, mechanical systems, electrical systems, and safety equipment. If you’re looking at a pre-purchase survey, expect to pay somewhere around $15-25 per foot of boat length. The whole thing usually takes 4-8 hours for your typical recreational boat, though I’ve seen some run longer when the surveyor finds surprises.

Types of Marine Surveys

Pre-Purchase Survey

This is the big one — the most thorough type of survey you’ll encounter. A pre-purchase inspection covers every accessible area and system on the boat to figure out the real condition and flag anything sketchy. I’ve used these reports to negotiate prices down more than once, and they’re invaluable for budgeting what repairs you’ll need after closing the deal.

You’ll also get a fair market value estimate in most cases, though keep in mind those numbers can swing depending on your local market and how familiar the surveyor is with your particular boat type. Don’t treat it as gospel — it’s one data point.

Insurance Survey

Your insurance company’s going to want a survey before they’ll write a policy or renew coverage on an older vessel. These focus more on seaworthiness and safety compliance rather than getting into every mechanical detail. Think of it as the insurance company making sure they’re not covering a floating liability.

Generally, an insurance survey is good for 3-5 years before they want a fresh one, but if your boat’s getting up there in age, they might ask for inspections more frequently. Just the way it goes.

Condition and Value Survey

These are basically cousins of insurance surveys but you’re ordering them for your own purposes — could be an estate settlement, financing, divorce proceedings, or honestly just wanting to know where your boat stands. It’s a solid way to get an objective third-party take on what your vessel is actually worth and what maintenance you should be thinking about.

Damage Survey

Had an accident or got caught in a nasty storm? A damage survey documents exactly what happened for your insurance claim and helps plan repairs. These are laser-focused on assessing damage extent and estimating what it’ll cost to make things right again.

Hull Inspection

Probably should have led with this section, honestly. The hull is your boat’s backbone, and it’s where surveyors spend a huge chunk of their time.

Fiberglass Construction

Here’s something I find fascinating every time I watch a surveyor work — they’ll tap the hull with a specialized hammer and just listen. A solid, well-laminated fiberglass hull has a distinct sound compared to the dull thud you get from delamination, water intrusion, or saturated core material. It’s almost musical when you know what you’re hearing. Problems that are completely invisible to your eyes show up immediately through sound.

Then there’s the moisture meter, which measures water content in hull laminates and cored panels. High readings are a red flag that means more investigation is needed. But here’s the thing — some moisture is perfectly normal in older boats. A good surveyor interprets readings based on the boat’s age, construction method, and where it’s been stored. Context matters a lot here.

Blister Assessment

Osmotic blistering is one of those things that keeps boat owners up at night, and it affects plenty of fiberglass hulls, especially older boats that live in the water year-round. Your surveyor will evaluate how bad the blistering is, talk through treatment options, and give you a cost estimate if it’s significant enough to warrant repair. Some blistering is cosmetic, some is structural — knowing the difference is why you hire a pro.

Structural Elements

Stringers, floors, bulkheads, transom cores — these are the bones inside your hull, and they get a lot of attention during a survey. They’re absolutely critical for hull integrity, but they’re also frustratingly prone to water damage, rot, and delamination. If your surveyor finds soft spots, cracking, or separation in these areas, you’ve got a repair conversation ahead of you. Not always a deal-breaker, but you need to know what you’re dealing with.

Keel and Rudder

For sailboats especially, the keel gets scrutinized for any movement, corrosion at the attachment points, and the condition of the fairing. Rudders are tested for play in the bearings, blade condition, and whether they operate smoothly. These components aren’t just about performance — they’re safety-critical. A keel bolt issue is something you absolutely don’t want to discover the hard way.

Deck and Superstructure

Deck Core Condition

Cored decks are fantastic for reducing weight, but they’ve got an Achilles’ heel: water intrusion. When the bedding around deck hardware fails, water seeps in and rots wood cores or causes foam cores to delaminate. Surveyors probe around every fitting they can reach and test deck stiffness across all accessible areas. You’d be amazed how spongy a deck can feel when the core’s gone bad — it’s unsettling to walk on.

Hardware and Fittings

Every cleat, rail, windlass, and piece of deck hardware gets checked for security and corrosion. That’s what makes proper bedding endearing to us boat buyers — it’s the invisible detail that keeps water from destroying everything below the surface. When a surveyor finds deteriorated sealant around fittings, it often points to bigger deck problems lurking underneath.

Windows and Hatches

Glazing condition, seal integrity, frame security — all of it gets scrutinized. Leaking hatches and windows are incredibly common complaints, and they cause interior damage that adds up fast. They’re also a strong indicator that maintenance has been neglected, which tells your surveyor a story about how the previous owner treated the boat.

Mechanical Systems

Engine Inspection

Engines are where things get really interesting, at least for me. Surveyors look for oil and coolant leaks, check belt condition and hose deterioration, and inspect electrical connections. The real gold, though, is oil analysis — they’ll pull a sample and send it to a lab where it reveals internal wear conditions that you’d never catch with a visual inspection alone. Think of it as a blood test for your engine.

The sea trial puts everything to the real test. Engines get run under actual load while the surveyor checks performance, listens for unusual sounds, watches exhaust color, and monitors temperature readings. They’ll note the maximum RPM achieved and compare it against what the manufacturer says you should be seeing. If there’s a gap, something’s off.

Drive Systems

Whether it’s stern drives, outdrives, or shaft systems, your surveyor’s looking for play, corrosion, and proper operation. One trick I learned is paying attention to the gear oil analysis — water in the gear oil means seal failures, and that’s something you want dealt with immediately. Not a “get to it next season” kind of problem.

Steering and Controls

Steering systems get tested for play, binding, and responsiveness. Control cables are inspected for fraying and stiffness — old cables can get sticky in ways that make boat handling unpredictable. Hydraulic systems get checked for leaks and proper fluid levels too. None of this is glamorous, but it’s all stuff that keeps you safe on the water.

Electrical Systems

Wiring Assessment

If you’ve ever seen a rat’s nest of wiring behind a boat’s electrical panel, you know why this section matters. Surveyors examine all accessible wiring for proper gauge, connection quality, and code compliance. Marine electrical systems face corrosion challenges that land-based systems don’t deal with, and shoddy installations create genuine safety hazards. I’ve seen boats where previous owners did their own wiring “upgrades” that made the surveyor visibly nervous.

Battery Systems

Batteries get evaluated for condition, whether they’re properly secured (loose batteries on a boat is a nightmare scenario), and whether the charging system actually works right. Load testing confirms your batteries can deliver the juice you need for starting and running your house systems when you need them.

Shore Power

Shore power connections, isolation transformers, and AC distribution panels all get attention because improper AC systems on boats can literally kill people. Electrocution hazards in marina settings are a real thing, and fire risks from bad wiring are no joke either. This is one area where you really want everything done by the book.

Safety Equipment

Required Equipment

Life jackets, fire extinguishers, visual distress signals, sound-producing devices — all checked against current Coast Guard requirements. Surveyors will flag anything that’s expired or doesn’t meet the standard. It’s not exciting, but running afoul of the Coast Guard on a safety check is an easily avoidable headache.

Navigation Lights

Every nav light gets tested for proper operation and correct visibility angles. Sounds minor until you realize improper lighting at night creates collision risk and puts you on the wrong side of legal liability. Quick fix if something’s out, but it needs to be noted.

Bilge Systems

Bilge pumps, high-water alarms, and through-hulls are all examined to confirm they work as intended. Adequate bilge pumping capacity isn’t optional — it’s what stands between you and a very bad day. I always ask surveyors how the bilge looked overall, since it tells you a lot about how a boat’s been maintained.

Sea Trial

Underway Testing

Any competent survey includes a sea trial, and honestly, it’s the part I enjoy the most. This is where every system gets tested under real operating conditions instead of sitting at the dock. Engines run at various speeds, steering gets tested under load, and all the instruments are verified against what’s actually happening. It’s one thing for everything to look okay on paper — it’s another to prove it works on the water.

Performance Verification

Surveyors compare what they observe against manufacturer specifications and similar vessels of the same type and vintage. If there’s a significant shortfall in performance, that’s a clear signal something needs investigating further. Don’t ignore those notes in the report — they’re telling you something important.

The Survey Report

Report Contents

A comprehensive survey report describes every system examined, all deficiencies found, and recommendations for repairs or further investigation. Most reports categorize findings by severity and safety impact, so you can quickly see what’s urgent versus what can wait. I like to read through the whole thing twice — once for the big picture, once for the details.

Using Survey Results

This is where the rubber meets the road for buyers. Pre-purchase survey findings are your negotiating leverage. Significant issues can justify price reductions, repair credits, or — and this is important — walking away entirely from a problematic boat. Don’t fall in love before the survey’s done. Minor maintenance items? Those are expected on any used boat, so don’t try to nickel-and-dime the seller over normal wear.

Take the time to review your report carefully and don’t hesitate to call your surveyor with questions about anything that doesn’t make sense. The good ones genuinely welcome those conversations and will give you clear, honest explanations of everything they observed. That’s what you’re paying for, after all.