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Mercruiser 5.0l, 5.7l Identification Tips

Repair Time: Less than 30 mins
Repair Difficulty: Easy
Mercruiser 5.0l, 5.7l Identification Tips
Mercury Marine I/O

Over the years there have been several changes to the GM 5.O-Liter and 5.7-Liter engine blocks. Often making it difficult to positively identify which version a technician is working on, and the appropriate parts required to complete appropriate service repairs. Hopefully, this will help to take some of the mystery out of the identification process.

1986 & Earlier
A. All 12 of the intake manifold bolts are installed at a 90-degree angle to the block.
B. The valve cover bolts are installed at the perimeter of the head.
C. Crankshafts utilize a 2-piece rear-main seal.
D. These blocks are machined to operate a mechanical fuel pump.
Note: In 1986 there was a limited production run with a one-piece rear-main seal, perimeter valve-cover bolts, and 90-degree bolt pattern for the intake manifold.

1987 thru 19951
A. 8 of the 12 intake manifold bolts are installed at a 90-degree angle to the block. The other 4 bolts are installed at a 72-degree angle.
B. The valve cover bolts are install in the center of the head.
C. Crankshafts utilize a 1-piece rear-main seal.
D. These blocks are machined to operate a mechanical fuel pump.
Note: During 1996 and 1997 the 3S0-Magnum (carb) and a limited production of the S.7­Liter EFI throttle body utilized this (non-Gen+) designed roller-cam engine.

1996 & Newer (Gen+)
A. All 8 intake manifold bolts are installed vertically. (straight up and down)
See MerCruiser Service Bulletin # 97-1 for proper torque procedures and specification.
B. The valve cover bolts are installedl in the center of the head.
C. Crankshafts utilize a 1-piece rear-main seal.
D. Timing covers are plastic.
E. Engines are fit with electric fuel pumps.
Over the years there have been several changes to the GM 5.O-Liter and 5.7-Liter engine blocks. Often making it difficult to positively identify which version a technician is working on, and the appropriate parts required to complete appropriate service repairs. Hopefully, this will help to take some of the mystery out of the identification process.

1986 & Earlier
A. All 12 of the intake manifold bolts are installed at a 90-degree angle to the block.
B. The valve cover bolts are installed at the perimeter of the head.
C. Crankshafts utilize a 2-piece rear-main seal.
D. These blocks are machined to operate a mechanical fuel pump.
Note: In 1986 there was a limited production run with a one-piece rear-main seal, perimeter valve-cover bolts, and 90-degree bolt pattern for the intake manifold.

1987 thru 19951
A. 8 of the 12 intake manifold bolts are installed at a 90-degree angle to the block. The other 4 bolts are installed at a 72-degree angle.
B. The valve cover bolts are install in the center of the head.
C. Crankshafts utilize a 1-piece rear-main seal.
D. These blocks are machined to operate a mechanical fuel pump.
Note: During 1996 and 1997 the 3S0-Magnum (carb) and a limited production of the S.7­Liter EFI throttle body utilized this (non-Gen+) designed roller-cam engine.

1996 & Newer (Gen+)
A. All 8 intake manifold bolts are installed vertically. (straight up and down)
See MerCruiser Service Bulletin # 97-1 for proper torque procedures and specification.
B. The valve cover bolts are installedl in the center of the head.
C. Crankshafts utilize a 1-piece rear-main seal.
D. Timing covers are plastic.
E. Engines are fit with electric fuel pumps.
Note 1: During 1996 and 1997 the 3S0-Magnum (carb) and a limited production of the S.7­Liter EFI throttle body utilized the 1987 thru 1995 engine block as stated above.
Note 2: During 1996 the S.7-Liter MPI (multi-port fuel injected) engines were produced with a vapor separator and a mechanical fuel pump. For these applications we recommend using the Mercury Remanufacturing Pro-Series longblock # 860186ROS. During 1996 and 1997 the 3S0-Magnum (carb) and a limited production of the S.7­Liter EFI throttle body utilized the 1987 thru 1995 engine block as stated above.
Note 2: During 1996 the S.7-Liter MPI (multi-port fuel injected) engines were produced with a vapor separator and a mechanical fuel pump. For these applications we recommend using the Mercury Remanufacturing Pro-Series longblock # 860186ROS.

860186R5 - Mercury Marine Pro Series Longblock - 5.7L - Remanufactured

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