MJM 4 Diesel DPI

By Christopher Hughes


Welcome aboard the diesel-powered version of the impressive MJM 4 performance day yacht. We recently tested the MJM 4, looking specifically at her performance and handling as powered by the new Volvo Penta DPI advanced drives.

MJM 4 cruising
We begin our look out of the water, with Volvo Penta’s twin, counter-rotating Duoprop propellers. This next-generation design features a double hydraulic clutch pack that performed silky smooth and with zero clunking in our testing. With the trim and steering hydraulic, the control unit is mounted on the transom inside the engine compartment.

MJM 4 advanced drives

Twin Counter-Rotating Duoprop Drives

The DPI is a fully integrated package with the drive paired with the latest computer-controlled version of the 440-horsepower Volvo Penta D-6 inline 5.5-liter diesel engine. These drives are fly-by-wire and rigged with sensors and lots of anti-corrosion features we will get into in a follow-up review article.

MJM 4 volvo diesel

440-Horsepower Volvo Penta D-6 Inline 5.5-Liter Diesel Engines

Our test boat was MJM 4 hull #10 and she measured in with a length overall of 46′ 8″, a beam of 12′, and a draft of 42″ drives down, 28″ drives up. She carries 350 gallons of fuel and 90 gallons of fresh water.

Starting with the hole shot, she powerfully accelerated from 0 to 30 mph in 12 seconds and to 40 mph in 19 seconds. Wide open throttle topped out at 3800 RPM with a speed of 45.5 MPH. At 3000 RPM she averages an impressive 33 MPH, burning 28 GPH for an incredible efficiency of 1.2 MPG!
Turns were crisp and exceptionally smooth, as responsiveness to the helm is superb with little to no bleeding of speed, even hard over.

The sound levels, or the lack thereof, are impressive, emulating that of a muffled yet throaty muscle car. In the cockpit, we recorded a sound of 77 dba and at the helm, with the aft curtain removed only 73 dba.

The final test item was the joystick operation. Let’s just say that the DPI system scored some serious marks here. Inputs with the joystick need only be minimal as the responsiveness is on par with the Volvo Penta IPS system. Station keeping was spot on, holding compass heading and deviating from the position with less than 3 feet deviation.

The MJM 4 diesel is a very special performance yacht. A Carolina Downeast express design, all-weather / all-conditions capable, and four social zones that include an open bow, yacht accommodations, indoor/outdoor pilothouse, and a large cockpit. All in a highly efficient diesel package.

MJM4 Pilothouse
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