Category A “Ocean” Certification – What Does It Mean?


MJM made it a primary objective that all MJMs would be certified at the highest level of safety possible… which meant those models under 40 feet are ISO CE Certified Category B Offshore, while the 40z and 50z are Certified ISO CE Certified Category A Ocean. There are no other boats of their type, of any size, achieving this high level of offshore safety. In fact, in the worldwide database of the International Marine Certification Institute (IMCI), we have only identified two other models under 40-feet with this certification, both being heavy displacement trawlers. The former achieves this with a low vertical center of gravity and the latter with massive tonnage. What does ISO Certification mean and how should it affect one’s peace of mind on the water? Let’s take a look at the subject.

When the European Union started in 1998, a Recreational Craft Directive was developed to set design/building standards for recreational boats up to 24 meters (79 feet). New and used boats sold in Europe, including boats built in the U.S. or anywhere else being exported to Europe, had to be certified as complying with one of four design categories for seaworthiness. These categories are based on factors such as the wave height and wind speed a given design is capable of handling, plus hull scantlings/strength and stability.

In essence, the further offshore a vessel is expected to venture, the greater the requirements for the vessel’s construction strength, stability, reserve buoyancy, resistance to flooding, deck drainage, crew safety, and other seaworthiness criteria have to be. Let’s take a look at the four categories.

Computer design rendering of the MJM Yachts 50z.

Category A — Ocean – This is the category with the toughest standards and covers vessels 40’ and over designed to be self-sufficient for extended voyages. It is defined as the “category of boats considered suitable for seas of up to 23 feet (7 meters) significant wave height and winds of Beaufort Force 9 (41-47 knots) or less, but excluding abnormal conditions such as hurricanes.”

Category B — Offshore – These boats are designed to go offshore with the ability to handle winds up to gale force 8 of 40 knots, and seas up to 13 feet (3.96 meters).

This chart shows a boat’s displacement and the Angle of Vanishing Stability (AVS) as indicated on its Gz Curve.

The difference between Category A & B is shown in the above graphic, where Mass is tons and AVS is the Angle of Vanishing Stability when the boat goes upside down. Category A boats need to be to the right of and above the blue line and a Category B boats to the right and above the red line.

Category C — Inshore – These boats may venture away from the protected harbors, but within striking distance of home… operating in coastal waters or large bays and lakes with winds up to 27 knots with and significant seas 8 feet (2.44 meters) high.

Category D — Inland or sheltered coastal waters – These are your typical day boats, operating in protected harbors, small lakes and rivers with winds to Force 4 (up to 16 knots) and significant wave heights to 4 feet (1.22 meters).

Now This Is Important

While a builder may claim that a boat is designed to a certain standard, it doesn’t necessarily mean that it ends up being built to it, unless inspected and certified by an IMCI (International Marine Certification Institute) surveyor, AND the builder can show you this plaque affixed to a bulkhead.

Because the number of people in the boat can reduce stability, the plaque shows the max number of people for Category A conditions, which on the 40z is 16. That’s not a USCG limit for liability purposes at all times. That’s just for Category A conditions.

Good story here. When Bob Johnstone was told that the 50z could carry only 2 more people under Category A than the 40z (18 versus 16), he was concerned about losing a 50z sale to a 40z owner who was moving up, because he wanted to be able to take 20 or so friends on the ICW to eat at Coconuts Restaurant near Bahia Mar… and might be concerned about the liability. “No worries,” said the IMCI surveyor, “We can provide the 50z with a ‘B’ rating as well as an ‘A’ rating, showing he can carry 30 people…and if he’s just going down the ICW or close to shore, you can post a ‘C’ rating, too, showing a capacity for 50 people.” Bob thought was going a bit too far and was happy to settle with the following plaque for the 50z.

The MJM Yachts 50z cruising off the coast of Newport, Rhode Island, at 34 knots.

Impact on Design and Manufacturing?

MJM Yachts is dedicated to producing the safest, strongest and most durable yachts possible. For this reason, while those under 40 feet can only be rated “B,” each of our powerboats is designed and built to exceed small craft structural requirements for ISO Category A Ocean. ISO requirements for strength are based on a design’s top speed and the expected impact to be absorbed by hull bottom and sides, as well as decks, bulkheads, structural grid, and any part of the vessel’s structure. The laminate schedule and materials are then specified to meet such stringent requirements.

Hull core samples of an MJM 40z show solid centerline keel (left) and hull.

ISO standards for polyester or vinylester resin and the 50:50 glass-to-resin ratio are lower than those achieved on MJMs, built by Boston Boatworks. An MJM is built using a wet prepreg epoxy, Kevlar, Eglass and Corecell with a glass-to-resin ratio of 62:38. Epoxy is significantly more expensive, but 25% stronger, unlikely to crack with use, and is water-resistant… which is why epoxy is used to coat the bottom of boats suffering from osmotic blistering. The MJM is built right from the start!

The CAD drawing of the structural grid for an MJM 50z to be fitted with triple Volvo Penta IPS 600s

That’s Not All…

ISO CE certification also takes into account engine emissions. In a world where greenhouse emissions are taking their toll on our environment, this is an important point. Meeting strict ISO CE emissions standards is comparable to meeting similar U.S. CARB requirements.

Additionally, sound levels will come into play. Boats are limited to 75 decibels for a single engine and 78 decibels for twin, triple or quad installations from a distance of 25 meters.

Highest Standards for MJM Yachts

MJM meets and exceeds all applicable standards, because ISO CE standards are more stringent than those of the United States Coast Guard (USCG), American Boat and Yacht Council (ABYC), or National Marine Manufacturers Association (NMMA) which mirror ABYC.

Boats sold in the U.S. do not have to be ISO CE certified… which costs upwards of $20,000 per model. USCG regulations require safety items such as PFDs and flares, carrying capacity for boats under 26 feet (7.93 meters), and level flotation if swamped for boats 20 feet (6.1 meters) and under. ABYC has distributed American versions of ISO CE Standards and Recommendations…but, they are strictly voluntary. Most critically, there are no ABYC design categories to differentiate between boats of different capabilities suitable to differing sea and wind conditions.

NMMA certification in the U.S. requires only about 70% of the ABYC recommended standards. While most U.S. builders follow the ABYC standards, and indeed many exceed those required by the NMMA, they are not mandatory as is the case in Europe with ISO CE mark standards and don’t involve the cost and post-build survey inspection of ISO.


The MJM Category A Ocean certification ensures MJM owners are boating on a stronger, more stable yacht, designed and built to exceed the highest standards in the world. It means having the peace of mind that comes with knowing that should you find yourself in weather and sea conditions outside your prior boating experience, you will be in one of the safest powerboats in the world. At sea, that comfort is the most important form of comfort a yacht can have.

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