What a survey covers, what a sea trial proves, who pays for what, and how the two fit into an offer.
On any boat worth surveying, the offer comes first and is made subject to survey and trial. That phrase is what gives you the right to inspect the boat properly and to walk away, or renegotiate, on what is found.
What a marine survey covers
A full pre-purchase survey is done with the boat ashore, so the hull below the waterline can be examined. A surveyor will typically assess the hull and deck moulding, osmosis and moisture readings, keel and rudder fastenings, the steering and stern gear, through-hulls and seacocks, the rig and chainplates on a sailing boat, gas and electrical installations, and the safety equipment. On a wooden or steel boat the emphasis shifts to fastenings and plate thickness respectively.
What it usually does not cover is the engine internals. An engine survey is a separate job, often by a different specialist, and on a boat where the engine is a large share of the value it is worth commissioning.
What a sea trial proves
The survey tells you about the structure; the trial tells you about the systems under load. Expect to see the engine start cold, reach full operating temperature, run at cruising revs for long enough to matter, and make its rated revs at full throttle — a boat that will not reach maximum revs usually has a fouled hull, a damaged prop or a tired engine. Check the gearbox in both directions, the steering at speed, the autopilot, the instruments, and on a sailing boat every sail hoisted and reefed.
Who pays for what
The buyer pays for the survey and, ordinarily, for the lift and scrub needed to do it. The seller provides the boat and usually skippers the trial, and pays for the fuel used. Agree all of this in writing before anything is booked, because a disputed lift bill sours a sale that was otherwise going well.
Using the findings
Almost every survey on a used boat produces a list. The skill is separating the three kinds of item: things that make the boat unsafe or unusable, things that will need money within a season or two, and things that are simply the condition of a boat of that age. Only the first two belong in a renegotiation.
The usual outcomes are that the seller has the work done before completion, that the price is reduced by an agreed contribution towards it, or that the buyer accepts the boat as it is. If the survey turns up something structural, a properly worded offer lets you withdraw and recover your deposit.
Choosing a surveyor
Use someone accredited, independent of the seller and of the broker, and experienced in your type of boat — a surveyor who mainly works on production motor cruisers is not the right person for a classic wooden yacht. Ask to see a specimen report before you book: a good one is specific and photographed throughout, and you should be able to understand it without a translator.
