In thirty years as a Captain I have seen many boat purchase stories. Some end well. Many don't. The pattern that repeats itself almost every time is the same: someone buys a vessel without getting a survey, and a problem appears that the seller knew about — or suspected — and that would have been easy to detect with a professional inspection.

This article explains what a nautical survey is, how it differs from other types of reviews, when you should get one, and what a well-done inspection actually covers. This is not theory: it is what I apply when I carry out a survey in Chile.

What is a nautical survey?

A nautical survey (also called a pre-purchase inspection or marine survey) is a formal technical assessment of the actual condition of a vessel. It is not a quick look at photos or a general conversation about the boat: it is a systematic analysis of its structure, engine, systems and documentation, carried out by someone with real experience at sea.

The word "survey" comes from maritime English and is the term used by insurers, yacht clubs and marinas around the world to refer to this type of inspection. In Chile the term is relatively unfamiliar, but the practice exists in every mature nautical market.

Key fact: In countries like the United Kingdom, Australia and the United States, it is practically impossible to obtain marine insurance for a used vessel without an up-to-date survey. In Chile this practice is not yet standard, which paradoxically increases the risk for buyers.

Survey vs. purchase advisory: they are not the same thing

There is an important difference between a purchase advisory and a survey, even though both serve to protect you before you pay.

The purchase advisory is a first filter: we review the listing, the photos and the description of the boat together. I identify red flags, tell you what questions to ask the seller, and give you a general orientation on whether the boat is worth investigating further. It is useful and quick, but it is based on what the seller chooses to show.

The survey goes deeper. It involves a formal written report, a systematic review of all the boat's components — not just the ones the seller shows — and in the physical format, an in-person inspection where I check what cannot be seen in photos: the condition of the hull when hauled out, the state of the bilge, engine performance on a cold start, the standing rigging on a sailboat.

The practical rule I use: the purchase advisory is for filtering out quickly and deciding whether it is worth going further. The survey is for confirming or ruling out that decision with real evidence, before signing.

When you should get a survey

Whenever the value exceeds a reasonable threshold

There is no exact figure, but the rule I apply is: if the boat is worth more than you could afford to lose if the survey reveals a serious problem, the survey pays for itself. For mid-to-high-value vessels — a cruising sailboat of 30 feet or more, a 22-foot aluminium offshore powerboat, a motor yacht — the answer is almost always yes.

When the boat is from an unknown seller

Buying from a friend or from someone with a known history changes the context. Buying from a stranger on MercadoLibre or a nautical listing portal, with no references at all, is a gamble. The survey turns that gamble into information.

When the boat is over 15 years old

Vessels age in ways that are not always visible. A 20-year-old fibreglass sailboat may have advanced osmosis that does not show up in photos. An engine with 2,000 hours might be close to the end of its working life, or it might have 2,000 hours of rigorous maintenance. The difference between those two scenarios does not appear in the listing.

When the boat has been sitting idle for a long time

A vessel that has spent years ashore or tied up at a dock without moving develops its own problems: dried seals, hardened hoses, degraded antifouling paint, corroded electrical systems. All of that can be expensive to fix and is not always visible to the naked eye.

Real case: A client bought a 38-foot sailboat without a survey because the price seemed good and the seller was "friendly." On the first haulout he discovered advanced osmosis in the hull and a cracked engine block. The repair cost exceeded 40% of the purchase price. The survey would have cost a fraction of that.

What a proper survey covers

A professional survey is not a generic checklist. It is a review adapted to the type of vessel and its history. However, any serious survey must cover:

Online survey vs. physical survey

I offer two formats, because not every situation requires the same approach:

The online survey is carried out using the available documentation and photos of the boat. It is the logical first step for any vessel outside your city or when you need to decide whether it is worth travelling to see it. I deliver a report with my findings and a clear recommendation: proceed, negotiate the price, or walk away.

The physical survey is the in-person inspection. I carry it out at the vessel's location — afloat or hauled out — covering all systems with direct access. This is the recommended option for higher-value vessels where details that cannot be seen in photos can completely change the purchase decision.

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The survey as a negotiating tool

There is a use of the survey that many people overlook: negotiation. If the survey reveals problems — and it almost always reveals something — you have an objective basis to ask for a price reduction. A report documenting that the engine needs attention, that the bilge has moisture, and that two shrouds have internal corrosion is not a reason not to buy: it is an argument to lower the price by exactly the cost of the necessary repairs.

In my experience, the cost of the survey is frequently recovered through the negotiation alone, in addition to avoiding surprises after the purchase.

What the survey cannot guarantee

A survey is an assessment of the vessel's condition at the time of inspection, with access to what is physically accessible. It cannot guarantee that the engine will not fail the following week, nor can it detect problems hidden behind sealed linings or in areas with no access. It is an information tool, not a guarantee.

What it does guarantee is that a professional with real experience at sea reviewed everything that could be reviewed and gave you their honest assessment. Before a significant purchase, that is worth a great deal.