Inflatable boats and rigid inflatable boats (RIBs) sit at the working end of the marine market: rescue craft, patrol boats, survey tenders, dive support and ship-to-shore transfer. They are also a category where product descriptions are loose and compliance claims are easy to make, because a boat can look right and still be built to the wrong standard. The ISO 6185 series is a key international reference for small inflatable craft, while SOLAS rescue boats follow a separate approval route.
ISO 6185-3:2024 for powered inflatable boats under 8 meters
ISO 6185-3:2024 specifies the minimum safety characteristics required for the design, materials, manufacture and testing of inflatable boats and rigid inflatable boats with a hull length of less than 8 meters and a motor power rating of 15 kW or greater. It covers two types: Type VII boats, fitted with buoyancy tubes on the port and starboard sides and suitable for design categories C and D, and Type VIII boats, similarly fitted and suitable for design category B. It applies to boats intended for operation between −20 °C and +60 °C (ISO 6185-3:2024).
The exclusions are as informative as the inclusions. The standard excludes single-chambered boats and boats with tubes made from unsupported materials, and it does not apply to aquatic toys or inflatable liferafts. It also excludes boats with tubes made from aluminum, rotomolded polyethylene, fiber-reinforced plastic or other rigid materials (ISO 6185-3:2024). For a buyer, those exclusions are a quick way to check whether a claimed “ISO 6185” boat actually falls inside the standard at all.
ISO 6185-4:2011 for larger RIBs
ISO 6185-4:2011 covers rigid inflatable boats with a hull length between 8 and 24 meters and a motor power rating of 15 kW or greater, for Types IX and X, within an operating temperature range of −20 °C to +60 °C. Type IX craft have a buoyancy tube covering at least 85 percent of the port and starboard sides and are intended for inshore and sheltered waters up to design categories C and D, wind force 6 Beaufort and significant wave heights up to 2 meters. Type X craft have the same tube coverage and are intended for design category B, up to wind force 8 Beaufort and significant wave heights up to 4 meters, with a motor power rating of 75 kW or greater (ISO 6185-4:2011).
This part also excludes single-chamber boats, boats of less than 1,800 N buoyancy, and boats made from unsupported materials of more than 12 kN inflated buoyancy and powered by motors above 4.5 kW. It is not applicable to aquatic toys, nor to inflatable liferafts, which are specified in ISO 9650 (ISO 6185-4:2011).
SOLAS rescue boats: a different approval route
SOLAS Chapter III includes rescue boats among the appliances it regulates, and the technical requirements sit in the LSA Code (IMO, SOLAS). In the United States, 46 CFR 160.156-7 requires rescue boats and fast rescue boats to meet IMO LSA Code chapter V, the IMO Revised recommendation on testing part 1/7, 46 CFR part 159 and subpart 160.156. The boat must be operable by people wearing immersion suits, provide the specified visibility from the operator’s station, use steel, aluminum or fiber-reinforced plastic for major rigid structure, and use accepted buoyancy foam of 32 ±8 kg/m³ with all required voids filled (46 CFR 160.156-7).
That is a materially different regime from ISO 6185. A boat built to ISO 6185-3 or ISO 6185-4 has been assessed against a small-craft safety standard; a SOLAS rescue boat has been approved against the LSA Code and the flag state’s approval scheme. The two claims can coexist, but one does not imply the other, and an inquiry should say which regime the vessel has to satisfy.
Materials, tubes and buoyancy chambers
Both ISO parts treat chamber configuration and tube material as safety characteristics rather than styling choices: single-chambered boats are excluded, and unsupported tube materials are excluded from the part that applies to the boat in question. The practical checks are straightforward — how many independent buoyancy chambers the boat has, what the tubes are made from, how the chamber divisions are arranged, and whether the boat’s design category matches the water and weather it will actually see (ISO 6185-3:2024).
For SOLAS rescue boats, buoyancy is specified more tightly. The US rule requires buoyancy material accepted as meeting the IMO testing recommendation, with a density of 32 ±8 kg/m³, and requires all voids needed for positive stability and self-righting to be completely filled with accepted material (46 CFR 160.156-7).
Maintenance and in-service inspection
ISO 6185 addresses design, materials, manufacture and testing; it is not an in-service maintenance standard, so operators need a maintenance regime from elsewhere. For SOLAS craft, the US rules require the manufacturer’s onboard maintenance instructions to include inspection checklists, maintenance and repair instructions, a periodic maintenance schedule, a lubrication diagram, a list of replaceable parts, sources of spare parts and a log for inspection and maintenance records, and they require each appliance to be in working order before the vessel leaves port (46 CFR 199.190).
In practice, RIB upkeep concentrates on the things that degrade: tube pressure and valve integrity, seam and patch condition, UV exposure, buoyancy compartment access, engine and fuel systems, and the lifting or towing points. The owner’s manual should define the intervals, and the survey regime should be agreed with the flag state or class society where the boat is used commercially.
What buyers should verify
| Item | What to establish |
|---|---|
| Standard and part | Which ISO 6185 part applies, and the edition year, given the boat’s length and motor power. |
| Design category | The category the boat is rated for, and whether that matches the intended operating area and weather. |
| Chambers and tubes | Number of independent buoyancy chambers, tube material, and whether the boat is single-chambered (excluded from the standards). |
| Approval route | Whether the boat is offered as a SOLAS rescue boat, and if so which flag-state approval and LSA Code chapter V evidence applies. |
| Documentation | Test reports, material certificates, maintenance manual, spare-parts list and warranty terms. |
Where to start
Buyers can compare craft in the safety equipment category and review examples such as FRP rigid rescue boats and inflatable rescue boats when scoping a requirement. Setting out the intended service, design category, motor power, passenger capacity and approval route in the inquiry form gives suppliers a much better chance of quoting comparable boats.
The discipline is the same as for any safety-critical purchase: decide which standard and approval route applies before comparing prices, then check that the paperwork proves it. A RIB that looks the part but cannot demonstrate its category is a liability, not a bargain.
Sources
- ISO 6185-3:2024 — Inflatable boats, Part 3: boats under 8 m with motor power of 15 kW and greater (abstract)
- ISO 6185-4:2011 — Inflatable boats, Part 4: RIBs 8 m to 24 m with motor power of 15 kW and greater (abstract)
- 46 CFR 160.156-7 — Design, construction and performance of rescue boats and fast rescue boats
- 46 CFR 199.190 — Operational readiness, maintenance, and inspection of lifesaving equipment
- IMO — International Convention for the Safety of Life at Sea (SOLAS), 1974
