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.
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1.MC553-SB Thermostat base. Fits engines with log style manifolds. Fits small block GM, V8 305 - 350 cu.in.Replaces Mercruiser # 78984.

2.MC553-BB Thermostat base. Fits engines with log style manifolds. Fits big block GM 454 cu.in. Replaces Mercruiser # 78985.

3.MC55-TSB Top Cover. Fits small block thermostat housings. Replaces Mercruiser # 47441.

4.MC55-TBB Top Cover. Fits big block thermostat housings. Replaces Mercruiser # 47442.

5.143-DEG Thermostat element, 143º for raw water cooling. Replaces Mercruiser # 59137.

6.48818 Gasket, top cover to base for log style manifolds. Replaces Mercruiser # 27-48818. Use with MC553-SB or MC553-BB thermostat bases.




1. MC552-SB Thermostat base. Fits engines with center riser style manifolds. Fits small block GM, V6 and V8 305 - 350 cu.in. Replaces Mercruiser # 87290. Uses original Tee fitting.

2. MC552-BB Thermostat base. Fits engines with center riser style manifolds. Fits big block GM 454 cu.in. Replaces Mercruiser # 90736. Uses original Tee fitting

3.MC55-TSB Top Cover. Fits small block thermostat housings. Replaces Mercruiser # 47441.

4.MC55-TBB Top Cover. Fits big block thermostat housings. Replaces Mercruiser # 47442.

5. 41812  Gasket, top cover to base for center riser style manifolds. Replaces Mercruiser # 27-41812. Use with MC552-SB or MC552-BB thermostat bases

6.47508 Sleeve, thermostat element. Replaces mercruiser # 23-47508. Use with MC552-SB or MC552-BB thermostat bases.

7.47510 Gasket, sleeve to thermostat element. Replaces Mercruiser #27-47510. Use with MC552-SB or MC552-BB thermostat bases.

8.143-DEG Thermostat element, 143º for raw water cooling. Replaces Mercruiser # 59137.
 

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