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MJM 50z

MJM 50 Zing running in Weymouth, MA.

The MJM 50z has a distinctive personality, derived in equal measure from CEO Bob Johnstone’s knowledge of which features mean the most to the owners—ease of use, comfort, and pride of ownership—and Doug Zurn’s artful rendering of those features. This adventure in marketing and manufacturing began 13 years ago with the 34z. Johnstone wanted a motorboat that he and his wife Mary could enjoy together. It had to be light, handy, comfortable, and good-looking, but most important, easy for either one of them to handle solo.

Boston BoatWorks builds all of the MJM models, and uses pre-preg Kevlar and E-glass fabric over a Corecell closed-cell foam core. Pre-preg is shorthand for fabric that’s impregnated with epoxy resin during manufacturing. This thermoset resin transforms the laminate into a very durable, temperature-resistant, exceptionally stiff, and extremely lightweight structure. Vacuum-bagged pre-preg laminates avoid inconsistencies in the resin-to-fabric ratio, which creates a stronger and lighter boat.

MJM Yachts gets its engineering expertise from Burke Design. Owner Steve Burke works closely with Boston BoatWorks and Zurn Yacht Design, analyzing the kevlar/E-glass composite laminates and structure to ensure that they comply with the new ISO (International Organization for Standardization) small-craft structural requirements. He also coordinates the effort to obtain CE mark certification for the boat and its systems. The MJM 40z and the 50z are the only boats of their type to have an ISO rating of A Ocean. For extra protection against grounding or the sudden juxtaposition with a hard floating object, the MJM 50z has a solid fiberglass keel.


Johnstone’s insistence on easy handling, ease of use, and stimulating performance has kept his boats small. His product strategy, based on his experience with each model, has always been, What would I like? “If it doesn’t make sense to me,” he says, “why would it make sense to anyone else?” It is a philosophy that has always served him well.

What Johnstone would like isn’t possible without high-tech construction and intelligent design. All of the ingredients have to interact perfectly. The pride of ownership that he hoped to elicit in the owners of MJM boats starts with “timeless good looks,” as Johnstone describes the 50z. Her open bridgedeck, sheltered as necessary by roll-down Isinglass panels, gives the after half of the boat a lacy appearance. Johnstone refers to this as a flying bridge without the ladder. The 50z has a single-level deck from the transom to the cabin bulkhead, where a companionway grants access two steps down to the “great cabin,” a saloon with galley to port and dinette to starboard. The single stateroom, a master forward, is spacious and has details Johnstone likes, such as an easy chair.

Lightweight construction reduces the boat’s drag, letting the builder get the performance it wants with smaller engines. Smaller engines mean a further reduction in weight, giving the boat an even better power-to-weight ratio. Projections for the 50z indicated that she would burn 28 gallons per hour at a cruising speed of 25 knots.

Keeping top-hamper weight to a minimum lets the builder lower the boat’s COG, which enhances lateral stability. Johnstone knows from informal research that roll is among the most hated motions on any boat, so he learned about the Seakeeper gyro stabilizer, and tested a boat with one. That’s when he decided to make the gyro stabilizer standard equipment on the 50z.

The light weight of the 50z makes her handle like a sports car, while the hull design gives her
a very seakindly ride.

MJM Yachts, 401-862-4367;

  • : 54'10
  • : 15'0
  • : 3'10
  • : 35,000 lb.
  • : 500 gal.
  • : 150 gal.
  • : 2/435-hp Volvo Penta IPS600s
  • : $1.7 million
  • : 3/435-hp Volvo Penta IPS600s
  • : Volvo Penta IPS with 1.82:1 gear ratio
  • : Volvo Penta IPS600 T6 propset

*Range based on 90% of advertised fuel capacity. Test numbers provided by MJM Yachts.

RPM Knots GPH Range db(A)
600 4.8 1.1 1,964 64
1000 7.7 2.7 1,283 68
1500 10.9 9.2 533 72
2000 17.8 16.0 501 74
2500 25.6 27.5 419 77
3000 32.1 40.5 357 79
3500 36.9 60.0 277 84
3570 40.0 67.0 269 84
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