|Number of Cylinders||8 Cylinders|
|Cooling System||Raw Water|
|Weight (lbs/kg)||871.00 lbs / 395.08 kg|
|Length/width/height||32 x 30 x 22" / 814 x 740 x 559 mm|
|Full Throttle RPM||4400-4800|
Mercury Remanufacturing designed the 357 Alpha 4V to be an inexpensive direct replacement for V-6 and small-block V-8 engines in a sterndrive packaged with an Alpha drive. Because it’s equipped with a four-barrel carburetor, the 275-hp (205 kw) 357 Alpha 4V offers a power upgrade over production 350-cu. in. MerCruiser engines because they had two-barrel carburetors and made 250-hp (186.4 kw).
Numbers Game. The 357 Alpha 4V makes 275 peak horsepower and maximum torque is 355 foot pounds at 3600 rpm. The compression ratio is 9.4:1. It runs on 87 octane, and the alternator output is 65 Amps. Dimensions for the engine are 32” x 30” x 22” (81.4 cm x 74.0 cm x 55.9 cm) and it weighs 871 lbs. (395 kg). It’s compatible with Alpha drives with 1.47:1 gear ratios. 1.81:1 gear ratios can be used for high altitude boating at over 5000 ft.
Easy Access. When it comes to maintenance, Mercury Remanufacturing makes it easy on the 357 Alpha 4V. The steering reservoir and oil filter are front and center on the top of the motor and the gearcase tank and fuel-water separator are in reach on the front of the port side of the engine. Mercury uses its proven Thunderbolt V ignition with knock control.
Bored Out. The 357 moniker comes from the cylinders in the block being bored out to .040” when the engine is remanufactured. This cleans up the cylinder walls and increases displacement to 357 cu. in. (5.8 L). The extra displacement means more torque and that translates into better bottom-end power for quick acceleration and sporty hole shot for towing watersports.
Bigger is Better. In addition to the added displacement over a stock 350-cid (5.7L) engine, the 357 Alpha 4V gets its power increase from a four-barrel 750-cfm carburetor that has electric choke for easier starting. A four-barrel carb draws in more fuel to the engine’s combustion chamber and more fuel mixes with more air to create more combustion. As mentioned above, a production 350-cid engine usually has a two-barrel carburetor. The carburetor sits on top of an aluminum intake manifold with a brass water crossover to prevent corrosion.
Thorough Cleaning. The 357 Alpha 4V starts out as a used GM Marine iron block core that’s bored out to 4.040” and the piston stroke is 4.04’’ x 3.48” (103 mm x 88 mm). All blocks that are selected for remanufacturing are: inspected for cracks, oven baked to remove sludge, bathed four times and then the oil galleries are cleaned out with a power brush to ensure that they are unobstructed. Finally, the blocks go through a high-pressure wash so that all surfaces are like new.
Starting From Scratch. The first step in remanufacturing a 357 Alpha 4V is to line hone the block before the camshaft is inserted, the nodular iron crankshaft is placed in its position and the pistons and connecting rods are introduced. Crankshafts are ground down to the next size and polished to like new condition. Roller camshafts are inspected, machined and re-used when possible.
New Where Necessary. Some parts can’t be remanufactured so Mercury uses new stainless steel valves and springs, cast hypereutectic alloy pistons, rings, and bearings on the inside, and new valve covers, oil pans and water pumps on the outside.
Stringent Specifications. To ensure that all the fasteners are torqued to the proper specifications, Mercury Remanufacturing technicians use computer controlled torque and angle equipment for precise torque control. This keeps consistent pressure across the block and cylinder surfaces, which ensures that gaskets will seat properly and that the block and cylinder heads don’t warp.
$7,993.75 for a single 357 Alpha 4V sterndrive.Warranty
1-year Factory Backed Limited Warranty.
2 additional Years of Mercury Product Protection available.Observations
Producing 275-hp and 355 foot pounds of torque in a small-block, the Mercury Remanufacturing 357 Alpha 4V could be a good candidate for repowering a runabout, deckboat or pontoon in the under 25’ (7.6 m) range. The extra cubic inches will give the motor good bottom end power for a hole shot for watersports.
The four-barrel carburetor should keep the performance strong through the power curve and Mercury smartly added electric choke for smoother starting. Because the engine is considered a small block, it should deliver good fuel economy for a V-8.