Sierra 18-1903 marine port exhaust manifold for OMC Cobra V8 5.0L and 5.7L (305 and 350 cu in) V8 marine gas engines. GM/Chevrolet small block. Fits many OMC 1989 and earlier models with log style (end rise) manifolds. Comes with gasket set. Each purchase is for one port-side manifold. Find the starboard side here.

Riser mating bolt dimensions are 3-7/8" (98.4mm) by 2-19/32" (65.9mm) bolt center-to-center.

This part is new and high-quality cast iron construction. To determine if this is the correct replacement for you, look on your current part for casting numbers and match them to the cross reference below:

Cross Reference	Part Number
OMC	912442, 909279, 910144
Osco Motors	2442
Barr Marine	OMC-1-912442
Sierra Marine	18-1903
Aqua Power	5513
GLM Products	51420

About Sierra
Sierra provides premium-quality aftermarket replacements for over 6,000 marine parts, tools, and components. Sierra products are engineered to meet or exceed OEM standards, and stand up in harsh marine environments. Every new Sierra part comes with a limited lifetime warranty that covers the useful life of the product against any defects in workmanship and materials.

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