Straight Reducing Exhaust Bellows, 5" to 4" Blue Silicone Hump Hose w/o Clamps

Hump Hose Bellows provide flexible connectors for marine wet exhaust systems. They offer much greater tolerance to heat, misalignment, engine movement and vibration than rigid connectors, with significant savings in cost, parts, labor and space.

These Step-Up/Reducing 270V Series molded single hump exhaust bellows are made of Very High Temperature (VHT) Blue Silicone* blended with EPDM rubber with no textile reinforcement. This synthetic rubber blend is rated for use up to 350°F (177°C) max, continuous.
These bellows have excellent resistance to ozone, saltwater, cold, heat, and aging.
Exceeds SAE J2006-R1 and ABYC & NMMA P-1 exhaust standards.
270V Step-Up Exhaust Bellows provide a convenient way to connect exhaust system components with differing hose sizes. This most often happens when a component (such as a muffler) is upgraded or replaced.
While these adapters can be used to reduce, as well as step-up, the internal size of the system, it should be noted that engine manufacturers typically don't recommend reducing the hose size, as this can increase exhaust back-pressure, which can reduce engine horsepower output.

• Blue silicone/EPDM blended rubber bellows - rated -65°F to +350°F maximum, continuous with a 10-year warranty
• Available in 5 step-up sizes from 3" x 3-1/2" to 6" x 8"
• Also available in straight versions; see Related Products
• Inlet/outlet cuffs are long enough to fit 2 hose clamps
• Note – Part #s ending in SS come with (4) wide stainless T-bolt hose clamps.


High Temperature Exhaust Hose Color Comparison
• Black exhaust hoses: made from molded, high temperature, black EPDM rubber. Rated -40°F to +250°F maximum continuous, with a 5-year warranty
• Blue exhaust hoses: made from a very high temperature, blue silicone rubber. Rated -65°F to +350°F maximum continuous, with a 10-year warranty
• Red exhaust hoses: made from an extra high temperature, red silicone rubber. Rated -65°F to +500°F maximum continuous, with a 10-year warranty

The addition of multi-ply fabric reinforcing enhances a hose's pressure resistance for coolant, turbocharger, and other higher pressure applications.


*Silicone rubber's outstanding characteristic is its resistance to higher temperatures, as well as having a longer service life than EPDM. Silicone hose is compatible with water and anti-freeze/coolants.
By comparison, EPDM (Ethylene Propylene Diene Monomer, commonly referred to as EPDM or EPDM rubber) can withstand modestly high temperatures and exhibits excellent resistance to environmental factors such as Ozone, UV, acids, bases, and general weathering.
Neither of these synthetic rubbers is compatible with fuel or oil, so be careful to protect from exposure.