Replacing Your 7.4 Liter Marine Engine Long Block
TERMINOLOGY:
There are three different types of marine 7.4L 454 cid engines. Some of the engines are interchangeable with only a few changes. NEW long block engines are available only for 1987 and up big block engines. If you are replacing a pre-1987 "Mark IV" engine and you are looking for a direct replacement you will need to purchase a remanufactured long block.
MARK IV - Up through 1986
> 12-3/4" Flywheel
> Mechanical Fuel Pump Mounts on side of engine block
> Stamped Steel Valve Covers
Gen V - 1987 Through 1996
> 14" Flywheel
> No mechanical Fuel Pump mounting pad
> Cast Aluminum Valve Covers
Gen VI - 1996 Through 2002
> 14" Flywheel
> No mechanical Fuel Pump mounting pad
> Cast Aluminum Valve Covers
> Roller Lifters
**For info on how to positively identify your big block engine, see article near the bottom of the page.**
7.4L L29 MPI 1998-2001 
This long block engine was used only with a General Motors installed multi-port injection (MPI) fuel delivery system. The long block utilizes a 1 piece rear main seal, roller camshaft, and oval port heads. The engine is rated at 330 hp but is not an actual produced power number. The actual horsepower value is about 305 hp. The engine does not include the intake, flywheel, and water pump. You must use an electric pump.
7.4L 330HP Power Package (JUST RELEASED)
PPT introduces the 7.4L Power-Pack, the repower package that gives you what you need. This Power-Pack is a NEW 330 horsepower GM Gen V/VI base engine, equipped with a complete fuel system as well as the ignition system. By using existing hardware, bellhousing and exhaust systems, installation is made simple.
7.4L 330hp 1987-2002
This long block engine was used with a 4 BBL carburetor, EFI (throttle body), and a Mercruiser factory installed multi-port injection (MPI) fuel delivery system. It has a 1 piece rear main seal, roller camshaft, and oval port heads. This engine can be used for pre-1987 applications but a modification must be made for the electric fuel pump. The engine does not include intake, flywheel, or water pump.
454 MAG 385 hp 1987-2002
This is the best way to distinguish it from the other 7.4L engines is that it has rectangular port heads and a high performance camshaft. They are the same heads that are used in the 8.2L 502 cid engine. The engine has a 1 piece rear main seal, roller camshaft, and must use an electric a fuel pump. The engine does not include an intake, flywheel, or water pump.
454 MAG 392 Hp Power Package (JUST RELEASED)
This Power-Pack is the perfect repower option for pre-1992 base 7.4L applications or for even for 1992 and up applications looking to upgrade from a 310/330HP 7.4L to the higher HP and higher torque 454 MAG 392 HP engine. Equipped with a complete fuel system as well as the ignition system. By using existing hardware, bellhousing and exhaust systems, installation is made simple.
502 mag 415 Hp
This engine uses the same heads that are used with the 7.4L 454 cid magnum engine (rectangular intake port). The engine has a 1 piece rear main seal, roller camshaft, and must use an electric a fuel pump. The engine does not include an intake, flywheel, or water pump.
502 MAG 415 Hp Power Package (JUST RELEASED)
This Power-Pack is the perfect repower option for pre-1992 base 7.4L or 502 applications or for even for 1992 and up applications looking to upgrade from a 310/330HP 7.4L to the higher HP and higher torque 502 MAG 415 HP engine. Equipped with a complete fuel system as well as the ignition system. By using existing hardware, bellhousing and exhaust systems, installation is made simple.
PPT offers New & Remanufactured 7.4L, 454 Mag and 502 Marine Engines
Partial Engine Packages (Longblock + Carburetor + Ignition)
Partial Engine Package Standard Rotation
Partial Engine Package Opposite Rotation
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