Most yacht tenders and many day boats are inflatables or RIBs, and the ISO standard they're built to depends on how much engine they take. ISO 6185 comes in four parts. The builder's plate tells you which applies, and that sets the boat's type, power limit and design category.
What it covers
In our words, from the published scopes:
| Part | Boats | Types |
|---|---|---|
| 6185-1 | Under 8 m, up to 4.5 kW, minimum buoyancy 1,800 N | I paddled, II powered up to 4.5 kW, III canoes and kayaks, IV sailing up to 6 m² of sail |
| 6185-2 | Under 8 m, 4.5 to 15 kW | V powered, VI sailing over 6 m² |
| 6185-3 | Hull under 8 m, 15 kW and more | VII for design categories C and D, VIII for category B |
| 6185-4 | RIBs with a hull of 8 to 24 m, 15 kW and more | IX for categories C and D, X for category B with 75 kW and more |
Part 4's scope describes Type IX as for inshore and sheltered waters up to wind force 6 and significant wave heights up to 2 m, and Type X as up to force 8 and 4 m, with a buoyancy tube covering at least 85% of each side. All parts exclude liferafts and aquatic toys. Parts 1 and 2 exclude single-chambered boats, and the latest Part 3 also excludes rigid tubes of aluminium, polyethylene or fibreglass. The standards apply under the Recreational Craft Directive.
What surveyors check against it
The builder's plate. The ISO 6185 part, the type, the maximum engine power, the maximum load and persons, and the design category. An outboard bigger than the plate's maximum is a finding in itself.
The tubes. Seams, patches, abrasion, UV damage, and whether each chamber holds pressure. Note how many chambers there are.
Valves and fittings. Inflation and pressure relief valves, towing and lifting points, and the transom's attachment to the tubes.
The hull and transom on a RIB. Moisture in a cored transom and the outboard bolt holes. See wet transom core.
Citing it in a finding
Cite the plate and the part: "Builder's plate gives ISO 6185-3, Type VII, design category C, maximum power 30 kW. Outboard fitted is rated 44 kW, above the plate maximum. Fit an engine within the plate rating or obtain the builder's written approval." For older tenders without a plate, describe the type and condition and don't claim compliance.