Exhaust Systems - OEM Replacement Exhaust Systems

For more help in finding the right exhaust system for your OEM Mercruiser application, see our guide on Marine OEM Exhaust Systems, Manifolds and Risers / Elbows.

O2 Spacer, Stock Mercury Riser
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O2 Spacer, Stock Mercury Riser


O2 Spacer, Stock Mercury Riser

This Unique 1" thick adapter plate provides an installation option for retro fitting a Oxygen sensor and or air fuel ratio gauge for tuning purposes Into Mercruisers most common Wet Joint style exhaust manifold systems. The part is CNC machined from 6061 Billet Aluminum then Naval Spec Hard Coat anodized for corrosion resistance (Beware of inferior non-coated versions)

A unique feature of this adapter is the cooling parts that run along each side of the sensor maintaining consistent temperature of the spacer. Designed to accept all popular 18MM O2 Oxygen sensors.

  • Mercury 3 and 4" Riser Gasket(700-32080) 2 Required
  • Stainless Steel 18MM Oxygen Sensor Plug(620-50031) 1 Required

TECH NOTE: Will O2 Sensors Work In marine exhaust systems?

YES FOR TUNING but they have limitations as water / moisture is a byproduct of combustion. Often boaters find there is moisture in their exhaust system that have collected or made their way inside of what is better known as the "DRY" exhaust stream of their exhaust system. Anything from steam like to little water droplets about 1/32" all around the inside of the exhaust. This is because water IS a by product of combustion. same thing you see on a cold morning behind cars. sometimes you see water dripping out.

Don't take our word for it ask a real rocket scientist: https://www.grc.nasa.gov/www/k-12/airplane/combst1.html

This is why O2 Sensors are great for tuning but have a limited long term life span unless protected by Catalytic converters like on New Marine engine offerings. So you know gas is known as a hydrocarbon based fuel. And we all know what hydro means WATER.