Osco Marine Manifolds
Since 1932
OSCO Motors Co. has been in the business of providing boaters with a high quality, reasonable cost alternative to original manufacturer's equipment.
All manifolds come with a 3 year warranty and DO NOT include gaskets. Order gaskets and bolts separately. We stock all OSCO manifolds and ship the same day.
Click on the Picture or The Part Number to Check Price

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1. 9745 Manifold. Fits 229 and 262 cu.in. GM V6 engines. Replaces Mercruiser #’s 99745 and 99746.Fits both sides of engine. Use mounting kit 9745-MK.

2. 9745-MK Mounting Kit, manifold. Fits 9745 manifold. Includes CS-GH gasket and mounting hardware.

3. CS-GH Gasket, manifold to cylinder head. Included in 9745-MK mounting kit. Replaces Mercruiser # 27-99757.

4. 4354 Riser, 4" exhaust outlet, 7º down angle. For late model inboard/outboard and inboards.
Replaces Mercruiser # 44354, 807914 and 807988. Use mounting kit 4354-MK.

5.4354-MK Mounting Kit, riser. Fits 4354 riser. Includes 8503-GR gasket and mounting hardware.

6. 8503A Riser, 3" exhaust outlet, 15º down angle. For early model inboard/outboards. Replaces
Mercruiser #’s 98503 and 98504. Use mounting kit 8503A-MK.

7. 8503A-MK Mounting Kit, riser. Fits 8503A riser. Includes 8503-GR gasket and mounting hardware.

8. 8503-GR Gasket, restrictor. Fits center riser Mercruiser. Common use is on all raw water cooled motors.Restricts flow, creating water back pressure to keep manifold and/or spacer full. Replaces Mercruiser # 27-41813.

9. 8503-GB Gasket, blocked. Fits center riser Mercruiser. For fresh water/closed cooling, gasket separates anti-freeze and raw water (no stainless plate required). Replaces Mercruiser # 27-41811.

10. 8503-GO Gasket, open. Fits center riser Mercruiser. Common use is at base of spacer block along with 8503-GR at riser. Allows spacer to fill with water. Replaces Mercruiser # 27-87105.

11. 3320 Spacer, 3" center riser. Fits 9745 manifold. Replaces Mercruiser # 93320. Sold each. Use mounting kit 3320-MK with 8503A riser or use 3320-MK-X with 4354 riser.

12 3320-MK Mounting Kit, spacer. Fits 3320 spacer with 8503A riser. Includes 8503-GO and 8503-GR gaskets and
mounting hardware to bolt 8503A riser and 3320 spacer to 9745 manifold.

13. 3320-MK-X Mounting Kit, spacer. Fits 3320 spacer with 4354 riser. Includes 8503-GO and 8503-GR gaskets and mounting hardware to bolt 4354 riser and 3320 spacer to 9745 manifold.

14. 3322 Spacer, 6" center riser. Fits 9745 manifold. Replaces Mercruiser # 93322. Sold each. Use mounting kit 3322-MK to mount spacer to manifold. Riser #’s 8503A or 4354 will require their own mounting kit.

15. 3322-MK Mounting Kit, spacer. Fits 3322 Spacer. Includes 8503-GO and 8503-GR gaskets and mounting hardware to bolt spacer to manifold. Riser #’s 8503A or 4354 will require their own mounting kit.

16.F68C9 Water Fitting, 90º elbow. 3/4" MPT x 1" hose barb. Replaces Mercruiser # 22-36305.

17. F68CS Water Fitting, straight. 3/4" MPT x 1" hose barb. Replaces Mercruiser # 22-45084.

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