Sea trial

A static inspection tells you what a boat is. A sea trial tells you how it behaves — engine response under genuine load, steering accuracy and feel, how systems cope when everything runs at once, and the noises and vibrations that simply do not exist alongside.

A trial with no independent surveyor aboard is a demonstration. With one aboard it is a test: the boat taken deliberately through the conditions that show how it behaves, and every observation recorded.

What is assessed

• Engine and propulsion — cold-start behaviour, warm-up, oil pressure and temperature under sustained load, ability to reach rated RPM, smoke character at load, cooling performance
• Transmission and drive — engagement, vibration through the range, shaft alignment symptoms, propeller behaviour astern
• Steering and handling — response, play, tracking, manoeuvrability at close quarters, autopilot function
• Systems under way — charging under real load, electronics and instrumentation, pumps, and anything that only misbehaves once the boat is moving
• Noise and vibration — characterised and located, since both are often the first symptom of a mechanical problem
• Sailing systems — on sailing yachts, time under sail whenever conditions permit: furling, winches and sail handling and, in a standalone trial, behaviour on each point of sail

Inability to reach rated RPM

One of the most common and most consequential findings is a vessel that will not reach its rated engine RPM. It can mean an over-pitched or fouled propeller, a tired engine, fuel delivery restriction, or a fouled hull — causes that range from trivially cheap to very expensive to fix. It is not detectable alongside, and it is one of the clearest arguments for attending the trial.

How it runs

Within a pre-purchase survey, one hour is included: enough for the items that matter most — machinery under load, steering, systems, and time under sail where applicable. A standalone trial typically takes two to three hours, depending on vessel size and what needs assessing. The approach is systematic observation with metrics documented as they are taken — temperatures, pressures, RPM against speed — rather than an impression formed and written up afterwards.

Conditions affect what can be established. A flat calm tells you little about how a boat handles a sea; a gale prevents proper engine assessment. Where they do not allow a representative trial, the report says so — and the trial is rescheduled, so that the result is one you can act on.

Standalone sea trials

A standalone trial is a different exercise from the hour within a survey: it is for learning the whole boat in depth. It is worth arranging to assess a yacht against a sailing programme or a specific intended use; to scope the work before a refit or a sail change, or to check the boat after a refit or major changes; where a previous survey excluded a trial because of weather, storage or scheduling; or where engine work or repairs need independent verification before payment is released.

An existing owner can also have performance checked against how the vessel behaved previously.

Findings are integrated into the pre-purchase survey report where the trial forms part of one, or issued as an independent written report where it does not.

Sea trial — FAQ→