If you're not big into boating, you might think of outboard motors as weedy, sputtering engines lumped on the back of tiny fishing dinghies. In reality, they're just as often horsepower monsters charged with shifting big boats at a rapid pace. Mercury is in the business of big outboard muscle, and its latest supercharged rig demonstrates that ably.
The new Mercury Racing V8 500R is named like a muscle car, and outputs 500 horsepower to match its moniker. The 4.6-liter V8 attains this figure with the aid of a bespoke Mercury supercharger, which provides a serious power boost as well as the characteristic whine of pulley-fed forced induction. It's built to run on 89-octane (95 RON) fuel, a touch higher than usual for an outboard to help cope with the boost.
The supercharger is all about getting more power out of a smaller package. "The 500R establishes a new benchmark for outboard power density,” said Stuart Halley, Mercury Racing general manager, adding “This motor offers incredible mid-range punch and pulls with unrelenting authority all the way to wide-open throttle."
Boosting the power to 500 horsepower over the previous 450R model took serious work. The new engine runs an upgraded crankshaft and bearings for better oiling, along with stouter 1-inch driveshaft splines. Connecting rods and pistons were also upgraded to help the engine reach its 6,600 rpm redline, while boost was turned up 26 percent compared to the 450R model. Other changes include an updated intercooler and a 15 percent larger throttle body to help suck down more air.
Brand new for the 500R is a new intake humidity sensor. This was implemented to allow the engine to make the maximum power possible in humid conditions. It's worth up to 30 horsepower in high humidity environments. The 500R also introduces a new gearcase that allows fitting props up to 17-inches in diameter. It's available in both R-Drive and R-Drive Sport configurations, designed for boats with top speeds up to 100 mph and beyond 100 mph respectively.
It's not the most powerful Mercury outboard; those honors still lie with the bonkers V12 models which deliver 600 horsepower. The 500R nevertheless delivers more power than the company's innovative V10s, however. A rare example of a V10 budget model, they put out 400 horsepower, with an eye to packing in more power in the same space as the company's naturally-aspirated V8s.
If you are desirous of a boat motor that can match the supercharged whine of your road-going muscle car, the 500R might just be the outboard for you. Be sure to explain at length to everyone on the lake about the benefits of forced induction as you wail on by at speed.
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