Attending your pre-purchase marine survey is one of the most educational days of your boating life. Understanding the four core phases of the survey enables you to prepare the boatyard, coordinate with the seller, and ask the right questions while the surveyor is inspecting the vessel.
Phase 1: Out-of-Water Hull & Running Gear Inspection
When the boat is hauled and suspended in the travelift slings or placed on blocking, the surveyor inspects the underwater surfaces:
- Acoustic Hammer Sounding: The surveyor systematically sounds the entire fiberglass hull below the waterline with a phenolic hammer. Clear, crisp rings indicate solid composite laminate; dull thuds indicate potential delamination, void spaces, or water intrusion.
- Moisture Meter Readings: Non-destructive electronic moisture meters (such as Sovereign or Tramex) are calibrated to identify relative moisture concentrations inside composite cores and transoms.
- Through-Hulls & Seacocks: Verification of marine bronze or composite valves, bonding wires, cotter pins, and smooth lever operation. Frozen or corroded seacocks are immediate safety hazards.
- Running Gear & Cutless Bearings: Checking propeller shafts for alignment, pitting, and bearing play. Inspecting strut bolts, rudder stocks, packing glands, and sacrificial zinc anodes.
- Osmotic Blistering: Cataloging bottom gelcoat blisters (size, fluid acidity, and distribution) across the hull surface.
Phase 2: In-Water Structural & Systems Examination
Once the vessel is placed back in the water, the surveyor moves inside to inspect internal integrity and ABYC compliance:
- Bilge & Stringers: Inspecting engine beds, bulkheads, tabbing, limber holes, and stringer caps for cracks, oil soaking, or detachment from the hull skin.
- Bilge Pumps & Float Switches: Testing primary and secondary high-water pumps, manual diaphragm pumps, and auditory high-water alarms.
- AC & DC Electrical Systems: Checking battery banks for tie-down security, terminal covers, master disconnect switches, reverse polarity indicators, and GFCI breaker protection in heads and galleys.
- Fuel & LPG Systems: Inspecting fuel tank labeling, corrosion on aluminum tank tops, fuel fill bonding, USCG-approved A1 fuel hoses, and LPG locker solenoid shutoff valves.
- Marine Sanitation Devices (MSD): Verifying USCG Type I, II, or III compliance, Y-valve lockouts, and holding tank condition.
Phase 3: The Operational Sea Trial
The sea trial tests the vessel under real dynamic loads on open water:
- Wide Open Throttle (WOT) Verification: Verifying that main propulsion engines reach manufacturer-specified rated maximum RPM without overheating or dropping oil pressure.
- Steering & Controls: Evaluating hydraulic helm response from stop to stop, electronic throttle shifts, autopilot tracking, and emergency tiller backups.
- Thermal Imaging: Scanning exhaust risers, heat exchangers, turbochargers, and electrical distribution panels with an infrared thermal camera to detect hot spots or cooling blockages.
Phase 4: Standing Rigging (Sailboats Only)
On sailing vessels, the surveyor inspects chainplates, swage fittings, turnbuckles, mast steps, and running rigging. Most insurance underwriters require complete standing rigging replacement every 10 to 12 years regardless of visual condition.
Do not hire a marine surveyor recommended solely by the selling broker. Hire an independent SAMS AMS® or NAMS-CMS accredited surveyor who represents your financial interests exclusively.