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.
Please Remember we stock parts and accessories for all makes and models of marine engines and boats. These catalog pages represent just a few of the parts we stock. Use the search field on the right to search by part the Part Number with the abbreviation at the bottom of each page. If you do not find what you are looking for please fill out the info form and we will find the parts you need and respond with a quote.
Click on the Picture or Part Number Below to Check price

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1.MO4-HOK Adapter Plate Kit. Converts large intake port manifolds to small intake port cylinder heads. Includes
MO4-HO adapter, MO4-GH gasket, MO4-HO-GH gasket and mounting hardware for Mercruiser manifolds.

2.MO4-GH Gasket, manifold to adapter

3.MO4-HO Adapter Plate. Can be used in other applications such as Marine Power, OMC, Etc.

4.MO4-HO-GH Gasket, adapter to cylinder head. New style high output head with small intake ports.

Note: Both elbow/reservoirs are made of cast iron like the original Mercruiser parts.
Osco does not make the 3.7L or 3.7LX exhaust manifolds.

1. 0879  Elbow/Reservoir. Fits Mercruiser cast iron manifold # 99908. Replaces Mercruiser # 90880.Cap included. Use mounting kit # 0879-MK. Fitting not included.

2. 0879-MK Mounting Kit, elbow/reservoir. Fits 0879 elbow/reservoir. Includes 0879-G gasket and mounting hardware.

3. 0879-G Gasket, elbow/reservoir. Fits 0879 elbow/reservoir. Included in 0879-MK mounting kit. Replaces Mercruiser # 27-97542.

4. 8561 Elbow/Reservoir. Fits Mercruiser aluminum manifold # 93174. Replaces Mercruiser # 98561. Cap included. Use mounting kit 8561-MK. Fitting not included.

5. 8561-MK Mounting Kit, elbow/reservoir. Fits 8561 elbow/reservoir. Includes 8561-G gasket and mounting hardware.

6.8561-G Gasket, elbow/reservoir. Fits 8561 elbow/reservoir. Included in 8561-MK mounting kit.
Replaces Mercruiser # 27-18272.

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