Cobalt 343 Concept Boat

The Cobalt 343 is a posh dayboat.

A gentleman’s high-performance boat, Cobalt’s 343 is a posh dayboat offering speeds in the mid-70s with the right power. Of course, being the fastest kid on the dock doesn’t necessarily mean you’re the coolest. That takes something more, something unique, which is why we tested the 343 in its Concept Boat configuration. Powered by twin 480-bhp Yanmar 6LY3 diesels turning surface-piercing props through innovative ZF Ring Drives, the 343 Concept Boat posted 62.5 mph at full throttle. More impressive is the extraordinary range this package delivers. The 343 Concept Boat will run twice as far as big-block gas-powered go-boats of similar weight and size. Plus it has that cool Ring Drive.

What’s a Ring Drive? It’s a surface drive turning through a two-speed, V-drive transmission. This shortens the installation, placing the engine above the drive unit and, unlike other surface drives, placing the props right at the transom instead of several feet aft. That’s my explanation anyway. Engineers say that the ring in Ring Drive refers to the robust mounting of this innovative system. Each transmission is bolted directly to the surface drive forward. Aft is a shaft bracket that supports the shaft strut and bearing. The engines are bolted directly to their corresponding transmission and shaft bracket. That’s the ring: engine, gearbox, shaft bracket. Since the shaft bracket and transmissions are mounted to a tunnel molded into the hull, no extra stringers are needed, which frees up engine space. And because all three drive train components are tied directly together-floating independently, if you will-keeping everything in alignment is a lot more likely than it might be on a fast boat with the 343’s rough-water joie de vivre.

What’s it like on the water? It’s slower to plane than a stern drive boat, but I kicked it into high gear at 2000 rpm and it was like switching the nitrous bottle open in a muscle car: Whoosh! Handling was crisp at all speeds, confirming that Cobalt’s stepped hull, with its flat keel pad, is user friendly. (I can’t say that about all stepped hulls.) Docking was a surprise. Docking a surface drive boat always gives me the willies, but with prop torque right at the transom, the Ring Drives allowed me to neatly spin the 343 into its slip. Goodbye Willies. Hello future?


The Highs: Gearbox and shaft all run in an oil bath, making the Ring Drive even more corrosion resistant than a stern drive. Rudders have less slop than stern drives so boat tracks straighter when landing after catching air. Cool as a cucumber.

The Lows: I found it impossible to throw the engine raw-water intake seacocks. Limber-hole alert: Water puddled between the outboard stringers and interior hull sides.

Toughest Competitor: This boat would appeal to those who are averse to stern drives, prefer diesel power, and want as much high performance as possible without forgoing luxury. It wouldn’t be a concept boat if there were another like it.

rpm knots mph gph naut. mpg. stat mpg. n. mi. range s. mi. range run angle sound level
900 3.9 4.5 1.8 2.2 2.5 391 450 0 77
1200 4.8 5.5 3.8 1.3 1.4 226 261 2 82
1500 5.6 6.5 6.1 0.9 1.1 167 192 2 82
1800 7.2 8.3 8.2 0.9 1.0 158 182 4 83
2100 7.6 8.7 10.9 0.7 0.8 125 144 4 81
2400 37.5 43.1 25.0 1.5 1.7 270 310 0 83
2700 41.6 47.9 29.5 1.4 1.6 254 292 0 84
3000 48.7 56.0 37.0 1.3 1.5 237 272 0 87
3250 54.3 62.5 52.0 1.0 1.2 188 216 0 89

LOA 37’2″

Beam 9’8″

Draft (max.) 3’1″


Displacement (lbs., approx.) 11,750

Transom deadrise 24.5o

Bridge clearance 5’9″


Max. cabin headroom 4’11”

Fuel capacity (gal.) 200

Water capacity (gal.) 10

Price (w/standard power) $229,249

Price (w/test power) n/a

Standard Power Twin 375-hp MerCruiser 496 MAG MPI Bravo One V-8 gasoline stern drives. ****

Optional PowerTwin gasoline stern drives to 1,150 hp total; twin diesel stern drives to 674 bhp gal.

Test Boat PowerTwin 480-bhp Yanmar 6LY3-STP in-line-6 diesel inboards with 354 cid, swinging 21¼ ” x 26″ five-bladed ss props through two-speed ZF Ring Drive surface drive transmissions with 1.6: 1 and 1.25: 1 reductions. ****

Standard Equipment (major items) GPS; AM/FM/10-CD remote stereo w/4 speakers; ss windshield frame; air compressor; enclosed head w/electric commode; dual battery system; trim tabs.