The Sea Trial Checklist Most Buyers Rush Through

The sea trial is the part everyone looks forward to and the part most buyers waste. Ninety minutes of driving a boat you are excited about, in nice weather, with the owner telling stories.

Then you buy it, and in July the temperature climbs at 3,800 RPM in a following sea because the heat exchanger is half blocked, and you find out that nobody ever held it at cruise for twenty minutes.

Treat it as a test, run in an order, with numbers written down.

What should you check on a boat sea trial?

The essentials, and the sequence matters because some of them are only available once.

Before anything: the cold start. Be at the boat before the seller starts it. A boat warmed up in advance hides hard starting, smoke on start, and low oil pressure at cold idle. If you arrive and the engines are already ticking over, ask for them to be shut down and left for an hour. If that is refused, note it.

Then, in order:

1. 01Cold start. How many seconds of cranking, what colour the exhaust smoke is and how long it lasts, whether it settles to a steady idle.
2. 02Idle in gear at the dock. Forward, neutral, reverse, both engines. Listen for clunks. Watch for vibration.
3. 03No-wake run. Steering lock to lock, count the turns, feel for play or notching.
4. 04Acceleration onto plane. Time it. Note bow rise and how long it takes to settle.
5. 05Wide open throttle. Hold it long enough to read stable RPM, speed and temperature.
6. 06Sustained cruise, minimum 20 minutes. This is the test that matters most.
7. 07Hard turns both directions at cruise, and a couple of crossings of your own wake.
8. 08Back down hard. Especially on a sportfish. Watch for water over the transom and for cavitation.
9. 09Dock work. Multiple approaches, both directions, and reverse steering.
10. 10At the dock afterwards, engines still hot: every remaining system.

The numbers to write down

Impressions are useless a week later. Record these.

Wide open throttle is the single most informative test on the list. If the engine cannot reach its rated maximum RPM range with a normal load aboard, one of three things is true: the boat is over-propped, the bottom or running gear is fouled, or the engine is down on power. All three are worth knowing and the first two are cheap to fix.

An engine that will not reach its rated band has been lugging for its whole life, and lugging is what carbons up a marine engine and eventually kills it.

What only shows up under sustained load

This is why the twenty minutes at cruise is non-negotiable.

• Cooling restrictions. A partly blocked heat exchanger or a tired impeller runs fine for eight minutes and climbs at twenty.
• Alternator and charging faults. Voltage that looks correct at first often sags once the alternator is hot.
• Fuel delivery problems. A failing lift pump or a restricted filter shows as a soft top end after fifteen minutes, not immediately.
• Exhaust leaks. Audible and sometimes visible only once everything has expanded.
• Transmission temperature, on inboards. It lags the engine considerably.
• Vibration from a slightly bent shaft or prop, which is often only obvious in a narrow RPM band you will not find in a short run.

The dock test afterwards, with everything hot

Do not let the trial end when you tie up. With the engines hot and the shore power on, go through:

• Every electronic: chartplotter, radar, autopilot, VHF on both a radio check and a DSC test, sounder, AIS.
• Air conditioning and refrigeration, which need time to prove themselves.
• Head and holding tank, including the macerator. Unglamorous and expensive when wrong.
• Windlass, all the way out and all the way back, watching the chain counter.
• Trim tabs, both independently.
• Generator, under load. Turn the air conditioning on while it runs.
• Bilge pumps, each one, manually and on the float switch.
• Shore power polarity and the galvanic isolator.

Then open the engine hatch and look at the engines hot. Fresh oil or coolant weeps show up much better on a hot engine than a cold one, and you have just given the boat the hardest hour it has had in months.

Bring the surveyor

Wherever possible, have the surveyor aboard. You will be driving and enjoying it; they will be watching gauges, listening to the exhaust note and feeling the hull. Most surveyors include trial attendance in their fee, and the observations they make under load are things a static inspection cannot produce.

Two people, two jobs. One drives, one watches.

An opinion about conditions

Sellers like a flat calm day and buyers usually accept one. If you can, trial the boat in the conditions you will actually use it in. A 26-foot bowrider that is lovely on a glassy morning can be genuinely unpleasant in a two-foot Chesapeake chop, and if that is your Saturday, you want to know before you own it.

I have never once regretted asking to go out in worse weather. I have several times regretted not asking.

After the trial

Write it up the same day, while it is fresh, with the numbers. If anything fell outside spec, get a quote before renegotiating — the same discipline that applies to survey findings applies here.

And if the seller will not permit a proper trial, at proper length, with a cold start and full throttle, that is not a scheduling problem. That is the answer.

Every brokerage listing we handle over 25 feet includes a recorded WOT figure and a cruise fuel burn taken at intake, so buyers arrive knowing what the boat should do before they spend a day finding out.