Yacht Sea Trial Checklist: What to Test Before You Sign

Quick answer: A yacht sea trial runs 3–6 hours for most vessels and tests engines at wide-open throttle, handling characteristics, all mechanical and electronic systems, and structural response under way. It is a mandatory pre-purchase step — always attended by the buyer’s independent marine surveyor. Findings during the trial can trigger a price renegotiation, a repair list, or a contract withdrawal.

See also: Yacht survey checklist · Yacht buying guide · Yacht closing process · Used yacht buying guide · Yacht flag registration guide

What Is a Yacht Sea Trial and Why Is It Non-Negotiable?

A sea trial is the underway performance and systems test conducted after the dockside survey and before you finalise the purchase. The marine survey — detailed in the Yacht Survey Checklist — tells you what the boat looks like standing still. The sea trial tells you what it actually does under power.

A surveyor with 30 years of experience put it this way: “I’ve surveyed boats that looked perfect on the hard and fell apart at 20 knots. The sea trial is where the boat can’t hide.”

No dockside inspection can reveal:

• Whether the engines perform to manufacturer RPM and speed specifications at wide-open throttle
• How the hull handles in a seaway, including any tendency to pound, hobby-horse, or show structural flex
• Whether the steering is responsive and the autopilot tracks correctly
• Whether the bow thruster, stern thruster, stabilisers, and trim tabs function properly under load
• Whether the propulsion noise or vibration suggests worn cutless bearings, propeller damage, or shaft misalignment
• How the electrical load behaves with all systems running simultaneously at sea

These are not minor concerns. A worn propeller shaft causing vibration can cost $8,000–$30,000 to address on a mid-size motor yacht. A main engine with declining compression delivering 8% below rated RPM may need a $40,000–$120,000 rebuild. Stabiliser repairs on a 65ft motor yacht can run $15,000–$60,000 depending on the system type. None of these defects are visible at the dock.

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Before You Cast Off: Dockside Pre-Trial Checks

The sea trial actually begins before leaving the berth. Conduct these dockside checks with the surveyor before starting engines:

Engine Compartment Pre-Start

• Inspect raw water sea cocks: open, functional, no weeping
• Confirm engine oil levels, coolant levels, gear oil in transmission
• Check bilge for water ingress or oil sheen — any fuel odour is a red flag
• Review engine hour meters and log the reading at the start of the trial
• Check engine mounts for cracking, deterioration, or missing bolts
• Inspect exhaust outlets: no black carbon scoring around exhaust ports
• Check fuel level and verify it matches the agreed fuel state in the contract

Dockside Engine Start

• Cold-start both engines (or single engine) — note start time, any difficulty starting, any smoke
• Black smoke at start: may indicate rich fuelling or worn injectors
• Blue-white smoke: may indicate burning oil — possible ring or valve seal wear
• Monitor engine temperature rise: should reach operating temperature within 10–15 minutes
• Check all engine alarm systems: oil pressure, coolant temperature, alternator charge

Electronics and Navigation Pre-Flight

• Power on all electronics: chart plotter, radar, depth sounder, AIS, VHF radio
• Confirm GPS signal acquisition and chart accuracy
• Test autopilot engagement from helm station
• Verify all instruments: knot meter/paddlewheel, wind instruments (sailing yachts), compass

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The Sea Trial: Phase-by-Phase Checklist

Phase 1: Departure and Low-Speed Handling (0–10 minutes)

Departure from the berth under controlled conditions reveals several critical systems:

Thrusters and manoeuvring:

• Test bow thruster: should produce vigorous thrust with no cavitation noise
• Test stern thruster (if fitted): equal response port and starboard
• Confirm thrusters work from helm station and, where fitted, from the flybridge

Propulsion at idle and slow ahead:

• Both engines engaged ahead and astern — no clunking, no delayed engagement in the gearbox
• Check for any vibration at idle-ahead speed: propeller shaft alignment indicator
• Confirm both bilge pumps activate on the auto float-switch and on manual

First visual check underway:

• Ask the crew to observe both engine exhausts from astern: should produce light grey exhaust at light throttle
• Check for any fuel or coolant leaking onto the water at idle

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Phase 2: Transition to Cruise Speed (10–30 minutes)

Advance throttles progressively from idle to cruise setting (typically 70–80% throttle).

What to observe:

• Both engines should reach cruise RPM within the manufacturer’s tolerance — typically within 3–5% of the published cruise rating
• Measure fuel burn rate if the vessel has fuel flow meters — compare to builder specification
• Confirm all engine temperatures remain stable in the normal operating range
• Check for vibration at cruise: any rpm-specific vibration bands suggest propeller damage, cavitation, or shaft whip
• Test steering response: helm input to vessel response should be proportional, without play or resistance

Trim tabs and stabilisers:

• Deploy trim tabs (if fitted) at cruise speed — confirm equal response port and starboard
• Engage gyro stabilisers or fin stabilisers if fitted — confirm reduction in roll
• Note any hydraulic noise, hesitation, or failure in the stabiliser system

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Phase 3: Wide-Open Throttle Test (WOT) — 20 Minutes Minimum

The WOT test is the most diagnostic phase of the sea trial. Run both engines at 100% throttle for a minimum of 20 minutes in calm conditions.

Record:

• Maximum achieved RPM on both engines (log separately)
• Maximum achieved speed over ground (GPS)
• Compare both to builder specification

Interpretation:

• WOT RPM within 3% of spec: normal — minor propeller pitch variation acceptable
• WOT RPM 5–8% below spec: investigate — probable causes include fouled hull, incorrect propeller pitch, or early engine wear
• WOT RPM over 10% below spec: significant defect — do not proceed without a full engine survey and compression test
• WOT RPM above spec: overpropped condition is unusual but possible — confirm propeller diameter and pitch

Smoke and exhaust at WOT — this is where sellers get caught:

• Light grey/white steam: normal in humid conditions
• Black smoke at WOT: injector or fuelling problem — expect a $3,000–$8,000 repair
• Blue smoke at WOT: oil burning — the engine needs a compression test and possibly a $40,000+ rebuild

One trick: if the seller “warmed up the engines” before you arrived, ask why. A cold start reveals starting issues, injector problems, and exhaust smoke that disappear once the engine is warm. Insist on witnessing a cold start — it’s the single most diagnostic 60 seconds in the entire sea trial.

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Phase 4: Systems and Safety Equipment Test (30–60 minutes)

While the vessel is underway at cruise speed, systematically test all onboard systems:

Navigation and communication:

• VHF radio DSC test call (to coast guard-approved test station, or internal radio self-check)
• Radar: confirm sweep, clutter filter, range rings, MARPA tracking if fitted
• AIS transponder: confirm MMSI, vessel name, and vessel type are correctly programmed
• Satellite phone or Inmarsat (if fitted): confirm connectivity
• Navigation lights: test all sectors — port, starboard, stern, masthead, anchor light

Safety equipment:

• EPIRB: confirm registration and battery expiry date — do not activate, visual check only
• Life raft: confirm canister hydrostatic release mechanism and service date (within 12 months)
• Fire extinguishers: confirm service tag within 12 months and appropriate class rating
• Flares: confirm within expiry date — flares expire at 3–4 years in most jurisdictions
• MOB (man overboard) devices: confirm horseshoe rings, throwlines accessible and undamaged

Deck systems:

• Windlass: raise and lower at least 5m of chain under power — check for any motor strain
• Winches (sailing yachts): power winches under load — no slipping or grinding
• Hydraulic systems: test all deck hatches, tender davits, passerelle/gangway under load

Accommodation and hotel systems:

• Air conditioning: cool-down test in at least one cabin
• Generator (if separate from main engine alternators): start under full hotel load
• Watermaker (if fitted): run a test cycle, confirm TDS (total dissolved solids) of output
• Refrigeration and freezer: confirm temperature maintenance under operation

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Phase 5: Sailing Trials (Sailing Yachts Only)

For any sailing yacht, the sea trial must include time under sail. Schedule the trial in a minimum of 10 knots true wind.

Sail handling:

• Unfurl headsail: confirm furling drum operates without grinding, no riding turns
• Hoist mainsail: test in-boom or in-mast furling if fitted — confirm full hoist and furl
• Upwind sailing: beat to windward for at least 20–30 minutes, observe pointing ability
• Off-wind sailing: reach and run under full sail, test spinnaker or asymmetric (if fitted)

Rig inspection under load:

• Have a crew member observe standing rigging from the deck under sail pressure
• Any vibration, movement, or noise from chainplates, mast partners, or keel bolts is a serious finding
• Check mast heel fitting for leaks into the interior
• Inspect running rigging: halyards, sheets, furling lines for wear under load

Performance benchmarks:

• Upwind: most sailing yachts of cruising design should achieve 40–50% of the true wind speed in boat speed
• Downwind in 15 knots: 7–9 knots for most modern monohulls is reasonable — verify against the designer’s polar data if available

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Phase 6: Return and Docking (30 minutes)

The return to berth reveals the final category of handling characteristics:

• Reduce from cruise to idle over a minimum of 5 minutes — observe temperature stability as engines cool under load
• Approach the berth at low speed under full engine and thruster control — note any hesitation or reduced thruster response when hot
• Shut down engines and note engine hour meter readings — log end-of-trial hours
• Allow engines to cool for 30 minutes, then re-check engine bays: any new oil weeping, coolant leaks, or unusual odours

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How Sea Trial Findings Affect the Purchase Agreement

Under the standard MYBA (Mediterranean Yacht Brokers Association) Memorandum of Agreement and the IYBA (International Yacht Brokers Association) Purchase and Sale Agreement used in the Americas, the buyer has defined rights based on sea trial findings:

Material defects found during sea trial: The buyer may:

1. Accept the vessel as-is at the agreed price
2. Request the seller to rectify specific items before closing, within an agreed timeframe
3. Negotiate a price reduction (credit at closing) in lieu of repairs
4. Withdraw from the contract and receive the full deposit refund if the defect is material and cannot be agreed

What constitutes a material defect:

• Engine performance below 8% of rated WOT RPM with no reasonable explanation
• Any thruster failure that cannot be demonstrated to be a minor electrical fault
• Structural cracking or flexing of the hull under way that was not disclosed
• Any navigation or safety equipment confirmed non-functional

Pricing impact of sea trial findings: Based on brokerage industry practice (not a guaranteed outcome), sea trial defects commonly result in:

• Minor maintenance credits: $500–$5,000 on vessels under $500K
• Moderate mechanical findings: 2–5% of purchase price as a credit or repair commitment
• Engine compression issues or major mechanical findings: 5–10% price renegotiation or seller repair obligation

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Specialist Surveyors for Larger Vessels

For vessels over 20m or any vessel where engine condition, classification compliance, or complex hydraulics are a concern, consider commissioning a specialist machinery surveyor in addition to your primary marine surveyor. Key specialisms:

• Machinery surveyor: engines, gearboxes, shafts, generators, hydraulics
• Electrical surveyor: DC and AC systems, shore power, inverters, battery banks, marine electronics
• Rigging surveyor (sailing yachts): aloft rig inspection, rigging swage assessment, mast step condition

Specialist surveyors typically charge $800–$2,500 per day depending on location and specialisation. On a $3M motor yacht, adding a specialist machinery surveyor at $1,500 is straightforward risk management.

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Sea Trial Checklist: Quick Reference Summary

Before departure:

• Engine oil, coolant, gear oil checked
• Bilge dry, no odour
• Hour meters logged
• Electronics powered and verified
• Safety equipment visual check complete

Low-speed and departure:

• Bow and stern thruster function confirmed
• Both gearboxes: ahead and astern engagement clean
• No smoke or unusual noise at idle

Cruise speed (70–80% throttle):

• RPM within spec
• Fuel burn within published range
• Trim tabs and stabilisers operational
• Steering responsive, no play

Wide-open throttle (minimum 20 minutes):

• WOT RPM logged and compared to manufacturer spec
• WOT speed logged via GPS
• Exhaust colour noted
• No abnormal vibration or temperature rise

Systems test underway:

• All navigation electronics confirmed operational
• Safety equipment dates verified
• Deck systems tested under load

Sailing (sailing yachts):

• Sail handling under load
• Upwind and off-wind performance observed
• Standing rigging checked under load

Return and docking:

• Hour meters logged at end of trial
• Engine bay re-inspected post cool-down

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Next Steps After the Sea Trial

A clean sea trial does not close the purchase — it removes the final technical obstacle. After the sea trial, the standard sequence moves to:

1. Survey report review — your surveyor delivers a written report within 5–7 business days
2. Negotiation of findings — any price adjustments or repair commitments are agreed in writing
3. Acceptance notice — buyer formally accepts the vessel subject to agreed conditions
4. Closing — funds transfer through escrow, title documents exchanged, flag registration updated

For a complete walkthrough of the closing process, see the Yacht Closing Process guide. For the documentation side of survey findings, see the Yacht Survey Checklist. For understanding total ownership costs once you take title, see the Yacht Ownership Cost Guide.

Topic	What to verify
Budget	Purchase price plus 10–15% annual running costs
Survey	Independent survey before deposit release
Flag	Registration and VAT status documented

Where this fits in the buyer journey

Use this Yacht Sea Trial Checklist 2026: What to Test Before You Buy page as one decision layer, not as a standalone verdict. Cross-check it against the ownership cost model, then pressure-test the numbers with the survey checklist. If the vessel profile still makes sense, send the brief through our matched shortlist request so we can route you to the right broker, surveyor, lender, or registration specialist for this exact case.

Buyer scenarios for sea trial checklist

Weekend coastal owner (sea trial checklist): Plan 40–60 sea days per year within 200 nm of home port. Prioritise simple systems, familiar yards, and insurance in a jurisdiction your lender accepts.

Liveaboard cruiser (sea trial checklist): You need passage-making range, comfortable berths, and predictable service networks in the Med or Caribbean. Budget 15–25% of hull value annually for running costs on this use case.

Charter-offset investor (sea trial checklist): You accept crew, management, and VAT/flag planning in exchange for limited personal weeks. Treat charter income as uncertain — never as guaranteed yield.

Apply this lens to yacht sea trial checklist before you sign any MOA or build contract.

Frequently Asked Questions

How long does a yacht sea trial take? +

A sea trial for a 30–50ft motor or sailing yacht typically takes 3–5 hours on the water. Larger vessels of 65–100ft usually require a full day. Superyachts over 30m often need 2–3 days for builder trials at build, and a 4–6 hour buyer's sea trial at resale. Plan at minimum 2–3 hours of underway time plus dockside checks.

Who should be present at a yacht sea trial? +

The buyer (or buyer's representative) and buyer's independent marine surveyor must both be present. The selling broker typically attends. The vessel's captain or regular operator should handle the helm unless the surveyor requests otherwise. A specialist machinery surveyor is strongly recommended for vessels over 20m or where engine condition is a concern.

What if a sea trial reveals problems? +

Under standard purchase agreements such as the MYBA MOA, the buyer can accept the vessel as-is, request specific repairs by the seller, negotiate a price reduction, or withdraw from the contract if defects are material. Most negotiations result in either a price credit or a specified repair list agreed before closing. Document every finding through the surveyor's formal report.

What speed should a yacht reach on sea trial? +

Compare actual WOT RPM and speed to manufacturer specification. A shortfall of over 5% on speed or RPM at WOT can indicate propeller damage, hull fouling, engine wear, or transmission issues worth investigating. Run at WOT for a minimum of 20 minutes to get a stable reading.

Do sailing yachts need a sea trial under sail? +

Yes. A sailing yacht's sea trial should include at minimum sailing upwind, on a reach, and downwind in at least 10–15 knots of true wind. Test furling systems, winches, clutches, traveller, and backstay tensioner. If conditions don't allow sailing during the scheduled trial, a re-trial under sail should be a contract condition before closing.

Can you waive the sea trial? +

Waiving the sea trial is a significant due-diligence risk and is generally not recommended for any vessel with mechanical propulsion. Remote buyers occasionally accept surveyor-only representation at sea trial, but this is not a substitute for the buyer or their representative being present. For new-build delivery, the builder's acceptance trial is required.

What documents should be verified during the sea trial? +

Before getting underway, verify: Certificate of Registry, Radio Licence with correct call sign, EPIRB registration, life raft service certificate, fire extinguisher service tags, engine hours on hour meter, and the fuel level agreed in the purchase contract. The surveyor's report becomes the formal record — log engine hour meter readings at start and end.