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Home Shop By Engine Parts & Anodes Engine Components Manifolds & Risers Barr Marine MC-1-47738 | Mercruiser Exhaust Manifold - Starboard Side
Barr Marine MC-1-47738 | Mercruiser Exhaust Manifold - Starboard Side
Barr Marine

Barr Marine MC-1-47738 | Mercruiser Exhaust Manifold - Starboard Side

SKU
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$726.00
$726.00 - $726.00
$726.00
$525.99
$525.99 - $525.99
$525.99
Availability Out of stock Lead Time Typically Ships within 1 Week In Store - Online Only - This item is stored in an external warehouse. Online orders will be shipped direct to the shipping address or available for in-store pickup typically within 1-3 days.
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Starboard side Exhaust Manifold with Rectangular bolt pattern riser for GM Mercruiser small block. Replaces Mercruiser B-47738A. Fits Mercruiser models: 225, 250, 255, 270, & 280TRS. Includes manifold to head gasket and mounting bolts, endplate gaskets, and raw water cooled riser gasket.


NOTE: Riser to manifold bolt pattern is "RECTANGULAR" 2-3/4" x 4-1/2". Made in USA, 3-year limited warranty.

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• Direct replacement Mercruiser GM small block log style exhaust manifold
• Port side or Starboard
• For Mercruiser 225 250 255 270 and 280 models
• Comes with gaskets and mounting hardware


Exhaust Manifolds, Risers and Elbows

Nearly every inboard and inboard/outboard (I/O) engine has exhaust manifolds and risers/elbows.

Given the harsh environment of high temperatures, saltwater and acidic exhaust gases in which these cast iron parts operate, their service life is often much shorter than most boat owners realize – often less than 10 years of regular engine use.

Exhaust manifolds and risers are large metal castings that carry hot exhaust gases away from the engine on inboard engines. All V-8 and V-6 engines, for instance, have a separate exhaust manifold along the side of each cylinder bank. The riser, which is often shaped like an inverted U, is located at the aft end, or centered on top, of the manifold. Sometimes the riser slopes down from the end of the manifold, if the engine sits high enough above the waterline, in which case it's often called an elbow. The exhaust hose is then attached to the aft end of the riser or elbow.

What makes these parts unique is that they're pipes within another pipe. This double-wall arrangement allows hot exhaust gases flowing in the internal pipe to be surrounded by cooling water in the external pipe, called a “water jacket”.
At the aft end of the riser, water from the water jacket combines with and cools the hot exhaust gases before continuing out via the exhaust discharge. Without the cooling effect of the water, the exhaust gas would overheat the manifold and risers, then burn through the exhaust hose in short order.

Keeping the water and exhaust gases separated until they exit the riser is crucial. If water finds its way into the gas-only chamber before the end of the riser because of a leak in the water jacket, it can seep into the cylinders when the engine is at rest and either seize the pistons with rust or create a "hydrolock" condition where the cylinders fill with water.

Brand: Barr Marine

WARNING: This product MAY expose you to chemicals, which are known to the State of California to cause cancer, birth defects and/or other reproductive harm. For more information go to www.p65warnings.ca.gov

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Backorder Policy: Occasionally, due to demand or supplier delays, some items may be temporarily out of stock or non-stock items. To ensure you can still get the products you need, you can order items even when they're out of stock. Our sales team will update you with the shipping lead time. Once back in stock, we promptly ship your item, and if your order includes both in-stock and backordered items, we may split the shipment. You can cancel your backorder before shipment, and request a refund to original payment method. For any inquiries, contact us at sales@freeportmarine.com.

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