Mercury Remanufacturing - 540 MAG Bravo 4V

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Captain's Report

Mercury Remanufacturing 540 MAG Bravo 4V

A displacement of 540 cubic inches gives the Mercury Remanufacturing 540 MAG Bravo 4V a torque advantage over engines with 454 or 502 CID.

Mission Statement

Mercury Remanufacturing developed the 383 MAG Stroker to replace most all 454 & 502 cu. in. engines in sport boats, performance and cruiser applications. This has been readily demonstrated in our recent tests. However, very large 36’+ boats and some customers simply demand bigger cubic inches. Mercury Remanufactuing has answered that need with a with the 540 MAG Bravo 4V. At 8.9L displacement, it’s a big V-8 designed to improve acceleration in offshore-style boats with Race-like performance while still providing the durability and affordability that owners expect in an every-day engine.

Mercury Remanufacturing 540 MAG Bravo 4V

The single-engine Baja 275 Performance ran faster with the 540 MAG Bravo 4V than it did when we ran it with a 496 MAG H.O. eight years ago.

A Big Block That Fits. Mercury MerCruiser still make new fuel-injected big block sterndrive packages in two horsepower ratings, the 8.2 MAG (380-hp) and 8.2 MAG H.O. (430-hp). Mercury Remanufacturing also offers a 496 HO MPI Plus Series engine rated at 425 HP. However, these fuel-injected big blocks may simply not fit into many older boats that were built around carbureted 454 & 502 V-8’s. Their tall intake manifolds & package width do not allow their installation into many pre-2000 hulls. The carbureted 540 MAG Bravo 4V uses a short-deck block that fits into older boats, and offers more cubic inch displacement. That is 540 cubic inches or 8.9L of displacement to be exact. That’s a lot. This large displacement delivers huge bottom-end torque (560 foot-pounds at 3500 rpm) and results in tremendous throttle response. By comparison, the older 454 & 502 big blocks will be absolutely blown out of the water because they only delivered 417 & 460 foot-pounds of torque respectively. The 540 big cubic inches produce 440 HP at a leisurely 4600 RPM, so it pulls hard without breaking a sweat.

Mercury Remanufacturing 540 MAG Bravo 4V

The 540 MAG Bravo 4V’s 4” flame arrestor and many other components on the motor are the same as those that were used on the carbureted Mercury Racing HP 500.

Strong Foundation. The 540 MAG Bravo 4V gets it’s displacement by boring the block to 4.50” and using a 4340 forged steel stroker crankshaft (4.25”). The special Mercury Remanufacturing crankshaft design doesn’t require a “tall deck” block. This keeps the installation size a match for the old 454-cid dimensions. The technique to neutral balance the engine is also unique, and results in a sophisticated idle that is not choppy. The compression ratio is a mellow 9.0:1. The cylinder deck is machined for flatness and the main bore is line-honed with new bearings. The extra-long connecting rods are forged steel and pistons a forged aluminum alloy.

Gas and Oil. Fuel and air are delivered to the combustion chamber through a Holley 800-cfm carburetor with electronic choke and a mechanical fuel pump sitting atop a single-plane aluminum intake with bronze crossover and pads. The 540 MAG Bravo 4V runs on 87-octane gasoline. A high-flow oil pump, copper oil cooler and oil thermostat keep the SAE 25W-50 synthetic blend racing oil flowing through the engine.

If the engine looks familiar to performance-boat enthusiasts, that’s because the oil cooler, the 4” flame arrestor, oil thermostat and serpentine belt system are all adapted from either the old MerCruiser Hi-Performance HP 500 & 500 EFI engines that made their debut in the 1990s, so the components are race proven.

Heads Up. Cylinder heads are remanufactured 454/502 heads with Manley extreme duty valves and a proprietary nickel/cobalt valve seat material that’s normally used in industrial engines or jet turbines. The remanufactured camshaft is a roller model from a 454/502-cid configuration. It has remanufactured stamped rocker arms, pushrods and valve covers.

Breathe Easy. Cast Iron exhaust manifolds with a 4” (102 mm) diameter have 316L dry joint elbows to ensure that the engine breathes freely and will last in a saltwater environment.

Modern Convenience. For easier maintenance, the 540 MAG Bravo 4V has a single serpentine belt, a multi-point drainage system with hand-removable blue plastic plugs and an easily accessed oil fill cap in the port valve cover.

Mercury Remanufacturing 540 MAG Bravo 4V

This installation drawing shows all the dimensions and the envelope in which the 540 MAG Bravo 4V will fit. Boat owners can find the drawing at
Mercury Remanufacturing 540 MAG Bravo 4V

The side view shows the clearance for the exhaust and flame arrestor and the required locations for the motor mounts.

Mercury Racing or Reman? Racing engines such as the Mercury Racing 520 could be potential candidates for similar repower projects, but that motor requires a new transom assembly and an upgrade to the Bravo XR high-performance drive. The retail price for this engine and drive package is $45,375. That’s over $90,000 for a pair of engines for an older boat that may not justify that price. The 540 MAG Bravo 4V retails at $16,993.75 per engine, and only the less-expensive Bravo X-Drives are recommended. This awesome value is what made the proposition to repower a 38 Scarab possible after sitting for 20 years. In that time there had simply not been a great repower option available like what the 540 MAG Bravo 4V delivers.

The Numbers

Wellcraft 38’ Scarab. We didn’t test the engines, but Mercury Remanufacturing had numbers from a recent re-power with the 540 MAG Bravo 4Vs in a 38’ (11.6 m) Scarab. With the twin 440-hp engines mated to Bravo One drives spinning 23” pitch stainless steel Mirage three-blade propellers through a 1.5:1 gear reduction, the 9,100-lb. (4,128 kg) boat ran 63 mph (54 knots) at 4600 rpm according to the Mercury techs. In acceleration tests, the boat hit 20 mph in six seconds and 30 mph in 10 seconds.

Mercury Remanufacturing 540 MAG Bravo 4V

The classic 38’ (11.6 m) Scarab is in great condition and now she has new reliable engines.

Baja 275 Performance. Mercury technicians tested a Baja 275 Performance single-engine sportboat with a 540 MAG Bravo 4V. Turning a 24” pitch Bravo One four-blade stainless-steel propeller through a 1.5:1 reduction, the 5,607-lb. (2,543 kg) boat hit a top speed of 64.3 mph (55.9 knots) at 4800 rpm and burned 44.5 gallons (168 L) of fuel per hour, giving her a range of 121.5 miles. Best cruise was 3000 rpm. The boat ran 38.1 mph (33.1 knots) and burned 17.5 gph, resulting in a range of 178 miles.

Our Archives. In 2007 we tested a Baja 275 Performance powered by a 425-hp MerCruiser 496 MAG HO Bravo One. It ran 61.4 mph (53.4 knots) and had a best cruise at 40.1 mph, which produced a range of 193 miles.


$16,993.75 for a single 540 MAG Bravo 4V.


1-year Factory Backed Limited Warranty.

2 additional Years of Mercury Product Protection available.

Mercury Remanufacturing 540 MAG Bravo 4V

The port engine shows how cleanly the 540 MAG Bravo 4V fits into the same spot that was previously occupied by a 454-cid engine. Notice the holes cut out of the engine hatch to save weight.


With the 540 MAG Bravo 4V, Mercury Remanufacturing gives owners of older performance boats and cruisers the one thing they’ve been craving -- bottom end torque. The old saying, “There’s no replacement for displacement” definitely applies to this 440-hp engine that produces a maximum of 560 foot-pounds of torque.

Mercury Remanufacturing designed the motor to be a gentle giant with a mellow compression ratio and a long stroke in a package that fits where a stock 454-cid engine would fit, making the engine a candidate for repowers with single-engine sportboats, twin- or triple-engine non-stepped V-bottoms and twin-engine cruisers.

Obviously, repowering is a big decision, but the price of the 540 MAG Bravo 4V and the torque and power that comes with it for the cost makes this engine an attractive one for owners who love the design and ride of their older straight-bottom offshore go-fast or cruiser.