These lightweight aluminum cowl louvers from Buckshot Racing #77 are designed for high-performance and outboard racing applications, including Mercury Racing 2.0, 2.4, and 2.5 outboards. They directly replace Mercury Racing 300 Drag & S3000 OEM part number 788582 and also fit some cowl assemblies originally supplied under part numbers 77376-2, 78858-2, and 78857-1 (check dimensions below).
These louvers can be used on performance and competition OMC, Yamaha, as well as Mercury V6 two-strokes, including 2.0L, 2.4L, and 2.5L platforms such as: 260 EFI, 280 ROS, SST-120, S3000, 300 Drag, Pro Max, Pro Stock, and other similar high-output race configurations. They are also applicable for F1H2O, OPC, APBA F200, USF1, and related V6 two-stroke competition categories.
The purpose of these louvers is to increase airflow into the cowl region and reduce thermal loading around the powerhead during extended high-RPM operation.
AL-6062 Marine Aluminum Construction
Each louver is produced from AL-6062 aluminum alloy. This magnesium–silicide alloy commonly achieves tensile strength values up to ~330 MPa and thermal conductivity in the 160–170 W/m·K range. This supports structural stability and also transfers heat outward through the louvers into the external airstream. Aluminum in this conductivity range does not trap heat the way polymer vents.
Each louver is precision-stamped using CNC-machined dies. This controls vent geometry, slat angle, and flow behavior. After stamping, each part is heat-treated to T6 temper to increase hardness and fatigue resistance under vibration, saltwater exposure, and thermal cycling.
A fine glass-bead texture is used to refine the surface; color options include anodized red, anodized blue, and anodized black.
Temperature and Horsepower Behavior in 2-Stroke Race Outboards
Two-stroke race outboards are sensitive to under-cowl temperature because the cowl interior is part of the intake path. When the air under the cowl is hotter, it is less dense. Lower density means less oxygen mass enters the cylinders per cycle.
A commonly used guideline is that every ~10°F drop in intake temperature increases air density by roughly 1%. In a high-specific-output Mercury V6 two-stroke (2.0L, 2.4L, 2.5L) a 1% density change typically corresponds to roughly a 1% change in potential power.
For reference, if an engine is making ~280 hp, 1% represents ~2.8 hp. If an engine is making ~300 hp, 1% is ~3 hp. That is enough to show up on the water as sustained pull or reduced fade in the last third of a straightaway.
Aluminum louvers additionally conduct heat outward due to higher thermal conductivity. Polymer vents do not. This is why aluminum louvers influence both airflow and heat removal inside the cowl.
Dimensions and Contents
Each set includes two (2) race cowl louvers.
Each louver measures 3" × 13.75".
Contact Mike Hill at +1-714-697-1716 or email mike@buckshotracing77.com for technical support.