What Is the Metal Hose on a Mercruiser from the Exhaust to the Intake Manifold?

Some boat engines have the same features as their landlubber cousins. For example, the metal hose from the exhaust to a Mercruiser intake manifold has the same function on land or at sea. Some people think it captures errant, unburned fuel in the exhaust and returns it to the carburetor. Nope. That nice, stainless steel conduit carries heat -- not fuel -- to the intake manifold, to keep it nice and toasty.

  1. Complete Combustion

    • Heat changes gasoline's viscosity, its resistance to flow. This means heated fuels flow with less resistance through the intake manifold and the carburetor's jets. The carburetor's jets atomize the heated gasoline the same way a pump-sprayer on a bottle of aftershave or cologne breaks the fluid into tiny droplets. The heated droplets of gasoline mix with the air more thoroughly than unheated gasoline and ensure more complete combustion. More complete combustion lowers the amount of unburned gasoline that makes it to the exhaust system.