Mercury Remanufacturing - 357 Alpha 4V
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.
The steering reservoir and oil filter are front and center on the 357 Alpha 4V.
Just a little bit lower to the left are the gearcase-lubricant reservoir and the fuel-water separator.
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.
The 357 Alpha 4V breathes new life into runabouts like this Stingray.
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.
The 357 Alpha 4V’s four-barrel carburetor helps give the motor spirited performance.
In addition to the larger cubic foot per minute rating, the carburetor has automatic electric choke for easier cold starting.
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.
The first step in the remanufacturing process is to bathe the engine blocks to clean all internal surfaces.
This power brush cleans out every oil gallery in the block so that the lubricant can get where it needs to go.
The final step in the cleaning process is a high-pressure wash.
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.
The block is honed in preparation for the crankshaft to be installed.
The cylinders on the 357 Alpha 4V are precision bored .040” over to provide clean internal surfaces.
The freshly polished camshaft is installed in the engine block.
The reground and polished crankshaft is placed in the block.
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.
New stainless-steel valves go into every remanufactured Mercury engine.
The pistons and rings are new, but connecting rods will be re-used if they fit specifications.
Since the valves are new, it makes sense to use new heavy-duty valve springs as well.
All gaskets are new to create a proper seal between engine components.
The piston and connecting rod assembly is introduced into the cylinder.
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.
This machine torques multiple studs or nuts at the same time to ensure consistent tightening.
Once all the studs are torqued, the machine paints a stripe on the fasteners to let technicians know where the engine is in the process.
Freshly machined cylinder heads are assembled with the new valves and springs.
If hydraulic lifters are used they are new, but roller lifters are hypersonically washed, tested for re-use and rebuilt.
New valve covers go on every remanufactured engine.
The high-capacity oil pan is also new, fabricated specifically for the 357 Alpha 4V.
A critical component on any marine engine, the marine circulation water pump, is also a new.
After the longblock is assembled, all engines are 100% hot tested, oil & water passages pressure checked, and a compression reading taken on all cylinder.
Whether it’s a deckboat, a pontoon or a runabout, the 357 Alpha 4V can improve its performance.
$7,993.75 for a single 357 Alpha 4V sterndrive.
1-year Factory Backed Limited Warranty.
2 additional Years of Mercury Product Protection available.
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.