18-1908K Manifold Riser Spacer Kit for Mercruiser Stern Drives

Replace corroded risers or increase riser height and hose clearance for inboard installations

Exhaust system components take a beating from prolonged exposure to salt and fresh water and being constantly heat cycled. As a result they corrode at a rapid rate. Replacement is not uncommon. If combatting back-flow or clearance issues on a new installation, a 3" extension can make a big difference.

These Sierra extensions provide the extra height to prevent water from traveling back into the riser when throttling down and they can also provide added clearance for exhaust hose routing. Engineered to be compatible with GM based V6 marine engines with 2 piece exhaust manifolds, these riser extensions feature machined mating surfaces that eliminate additional preparation to establish a proper seal. Each riser extension is leak tested prior to paint to ensure quality. Sierra uses special casting techniques to create risers with uniform wall thickness.

These kits have been assembled to eliminate extra time spent sourcing individual parts and include extensions, threaded rods, fasteners, gaskets and plugs for both port and starboard sides.

Sierra engineers parts to meet or exceed manufacturer specifications and has earned the confidence of engine manufacturers and technicians. Boaters and technicians can be assured of the fit and function of every Sierra part.

Key Features

• Engineered to meet or exceed OEM specifications
• Adds 3" of height to exhaust riser to prevent back-flow issues or add exhaust hose clearance
• Compatible with GM based V6 carb and TBI engines with 2 piece exhaust manifolds
• Kit includes extensions, threaded rods, fasteners, gaskets and plugs for port and starboard side risers
• Backed by SeaStar Solutions Limited Two-Year Warranty

 Sierra Part Number 18-1908K Application Table

The Sierra Engine Parts Selector

In addition to riser extensions, we offer a wide variety of other engine parts manufactured by Sierra. To see if we have the part you need, see our Engine Parts Selector, where you can search by engine make, serial number and model or year of manufacture.