This is the ballistic new Mercury Racing 450R outboard engine

Mercury boasts that the new Mercury Racing 450R has "the highest power to weight ratio of any outboard engine today".

The US outboard engine maker has already teased that up to six of the 450Rs can be hung off a transom and controlled by one throttle and steering wheel -- that's 2700hp in total.

The Mercury Racing 450R engine will be available here in limited numbers from early to mid next year, Mercury said, and available via Mercury Racing dealers only.

The new engine is "near the same weight" as the supercharged V6 Mercury Racing 400R, produces 40 per cent more torque than the 400R, and in the US will produce its performance on unleaded fuel. In Australia, peak performance will come from using 95RON premium unleaded fuel.

"We make what is intended for the few," Mercury Racing general manager Stuart Halley said. "This really is performance without compromise."

The engine is based on a quad-cam 64-degree bank 4.6-litre V8 with supercharged induction, and using the same powerhead as developed for the 4.6-litre naturally aspirated Mercury Racing 300R. Peak torque kicks in from around 4500rpm, with a linear increase from around 2000rpm, documents posted online show.

Boosting performance is a 2.4-litre belt-driven, twin-screw supercharger delivering "zero-lag pressure charging for instant throttle response".

"The water-cooled supercharger and twin charge-air coolers increase intake air density for higher torque," it said. "An electronic boost bypass valve automatically responds to changing conditions."

The engine is also fitted with what Mercury racing calls "Transient Spark", a pre-programmed timing advance that helps to optimise torque.

The engine is fitted with Mercury Racing's Sport Master gearcase that is rated for speeds of more than 140km/h. A 5.44HD gearcase is also available for "submerged applications".

The Mercury Racing 450R's midsection features heavy-duty guide plates and stiffened engine mounts to help with stability at speed. Twin-engine fit-outs can also use a rear tie bar to help with rigging.

It is also compatible with Mercury's Joystick Piloting for Outboards, which helps with low-speed manouvering for up to six outboard engines.

A more powerful turbocharged V8, producing at least 500hp, is still rumoured to be in the works.

As well as the joystick controller, Mercury Racing has equipped the 450R with Adaptive Speed Control that will automatically hold engine revs as load or conditions change, meaning less need to work the throttle controls.

The engine is even smart enough to increase its idling revs when needed to help charge batteries and run electronics.

And for those who like bespoke looks, Mercury Racing will allow its US customers to use an online outboard design tool to make their outboard engines stand out on the water.

Earlier this year, Mercury expanded its engine-making factory to allow it to “make complex blocks, driveshafts, and gearcases for Mercury outboards”.

“The addition will be filled with large tonnage die-casting equipment containing cutting-edge technologies that will drive higher quality and better throughput to keep up with increased engine demand especially with the V8 and V6 product lines,” it said.

Mercury’s new V6 engine range has been in high demand since it was launched early last year. The new engines initially were in such high demand in the US that Mercury’s Australian operations was forced to air-freight them in to meet orders.