Why a structured sea trial

A sea trial is where your repair either proves itself or fails privately, with you aboard instead of the customer's family. It's also a billable diagnostic product for pre-purchase inspections. Run the same structured trial every time so nothing gets skipped; a checklist on a clipboard also signals professionalism the customer remembers.

Before leaving the dock

• PFDs aboard and worn for the trial; kill lanyard attached to the operator
• Fuel adequate, bilge checked dry (baseline), battery voltage noted
• Engine cold-start behavior observed and noted (hard cold starts hide at warm restarts)
• Idle in neutral: rpm steady, alarms self-tested, charging voltage on the meter
• Shift engagement F-N-R at the dock: crisp, no grinding, reasonable clunk only
• Steering lock-to-lock while stationary: smooth, no binding, no fluid at the cylinder

Underway sequence

1. Idle out — watch temp rise to thermostat opening; note steering feel in gear.
2. Mid-range cruise — record rpm, speed, temp, oil pressure/volts. Listen: drivetrain rumble, gimbal chirp on turns (sterndrives), prop vibration.
3. Hard acceleration — hole shot clean? Hesitation (fuel delivery), ventilation (prop/hub), or clatter (detonation — back off immediately)?
4. WOT run — rpm must land in the service manual's window (see the prop article); note top speed, trim behavior, temperature stability over a sustained run, not a five-second blip.
5. Trim sweep at cruise — porpoising, chine walk, ventilation at high trim.
6. Hard-over turns both directions — prop blowout, cavitation noise, steering effort symmetric.
7. Back to idle — does it idle hot after load (cooling restriction tell)? Restart when warm.

Back at the dock

• Bilge re-check: what came in?
• Engine visual: leaks (fuel, oil, gear lube streak behind the drive), belt dust, weeping fittings
• IR gun across cylinders/risers for outliers
• Write it all down with numbers, not adjectives — "ran fine" is not a record; "5200 rpm @ 43 mph, 172°F stable" is

Common mistakes

• Trialing solo without anyone knowing where you are — file a float plan, even informally
• Letting the excited customer drive the WOT test
• Skipping the warm-restart test (the most common comeback complaint)
• No baseline numbers from before the repair to compare against

When to walk away

Weather, an overloaded boat, missing safety gear, or a customer who insists on riding along with kids during a first shakedown — reschedule. No invoice is worth a bad day on the water.