11/13/2025
In Stock now! The 4.2 SHO Billet intake-
Material and Construction:
Crafted from 6061-T6 billet aluminum and hard-anodized for durability, this intake replaces the factory plastic grate on the Yamaha SHO lower unit. The billet construction eliminates the risk of damage from overtightening and ensures long-term reliability.
Purpose and Design Intent:
This billet intake is designed to improve high-speed and shallow-water performance by allowing the engine to be used at a higher position. By placing the water pickup lower on the bullet nose, it reduces drag and maintains steady cooling flow even when the lower unit is trimmed higher out of the water.
Hydrodynamic Performance:
With two 0.5-inch diameter intake holes—one on each side—the intake achieves a combined water flow equivalent to a 1-inch diameter path. At speeds between 70 and 90 mph, it can deliver an estimated flow of around 40 to 50 gallons per minute. The Yamaha 4.2 Sho requires 20-30 gallons per minute to maintain normal operating temperatures at speed, so we size the billet intakes for the rated median flow of the poppet valves to manage accordingly.
Scoop Design and Debris Management:
The intake’s scoop is intentionally narrower at the front and wider at the back. This design minimizes the risk of debris or weeds packing into the intake, as any material that enters is deflected by a backward-angled wall. This prevents clogging and ensures that water, not debris, is funneled into the cooling system.
Pressure Relief Features:
To prevent over-pressurization at high speeds, the two small top holes act as pressure relief vents. They allow the engine to manage its own cooling without forcing open poppet valves. This ensures stable operating temperatures and prevents exceeding safe pressure limits, typically around 25 to 28 psi.
Additional Advantages:
Overall, this billet intake not only improves high-speed performance but also ensures reliable water flow at lower speeds and idling. It provides a durable, maintenance-friendly solution that won’t fail due to overtightening or wear, making it ideal for both performance and longevity.
