The Big Key from Buckshot Racing #77 Technical Insight: The Benefits of an Oversized Stainless Steel Keystock for Lower Unit Bearing Carriers. Replaces Part Number: 28-30281
When it comes to the structural integrity of Mercury 2.0, 2.4, 2.5, and 3.0 Liter outboard lower units, the key stock plays a critical role in transmitting torque while preventing the bearing carrier from spinning within the housing. A small enhancement in the key’s dimensions and material quality can improve durability, especially in performance environments.
Our stainless steel “Big Key” design that is 0.400 inches in length, compared to the traditional 0.250-inch keystock. This longer (+0.150 inches), dimensionally oversized (+0.003 inches) key offers significant advantages in shear strength, fit stability, and corrosion resistance.
The Big Key Stock replaces the Mercury Marine and Racing Bearing Carrier Machine Ket Stock OEM part number 28-30281, drag racers, high-performance boaters, enthusiasts, and outboard gearcase mechanics.
Shear Strength Comparison: Longer + Tighter Fit
The 0.400-inch Big Key provides a 60% increase in shear load capacity (5,000 pounds vs. 3,125 pounds) compared to the 0.250-inch keystock. This improvement reduces the likelihood of the bearing carrier spinning under heavy torque loads, especially in high-performance or demanding marine conditions.
Tighter Fit: Reducing Looseness and Play
In addition to being longer, the Big Key is designed to be slightly oversized by a few thousandths of an inch. This tighter fit ensures:
Better load distribution, reducing localized stress.
Minimized movement or play in the keyway can wear down components over time.
A tighter fit reduces the risk of the key shifting or deforming, ensuring a more stable connection between the shaft and bearing carrier. This design innovation makes the Big Key Stock a standout solution for lower unit durability.
Marine-Grade Stainless Steel: Corrosion Resistance
The Big Key is crafted from marine-grade stainless steel, known for its excellent resistance to:
Saltwater corrosion.
Oxidation in marine environments.
This ensures the key retains its integrity and load-bearing capacity over time, even in the harshest conditions. Traditional carbon steel keys may have higher shear strength but are prone to rust and degradation, making stainless steel the superior choice for long-term performance in lower unit applications.
By combining a longer length and tighter fit, the Big Key addresses common issues with traditional key stock on Standard Lowers, Sportmaster, CLE, and Coned Gearcases:
Reduces the chance of the bearing carrier spinning: Higher shear strength resists torque forces that would otherwise lead to failure.
Extends lower unit lifespan: Reduces wear and tear on the keyway and bearing carrier.
Improves reliability: Ensures a more stable and secure fit for high-torque outboard motors.
The 0.400-inch stainless steel Big Key (replace Merc Part Number: 28-30281) significantly improved over the traditional 0.250-inch key stock. Its increased length, tighter fit, and corrosion resistance make it an ideal solution for reducing the likelihood of bearing carrier failures in lower units.
With 60% more shear strength, the Big Key offers enhanced performance and durability, particularly for marine applications where reliability is critical.
For outboard motor enthusiasts, marine mechanics, and anyone seeking to improve the strength and stability of lower units, upgrading the 28-30281 to the Big Key Stock offered from Buckshot Racing #77 for your Bearing Carrier is a straightforward way to ensure peace of mind and long-term reliability, even in the toughest conditions.
Replacement Sportmaster Cover Nut 15840 in Billet coming soon.
Contact Mike Hill with any questions at +1-714-697-1716 or mike@buckshotracing77.com
11405
18-2376
73020A20
775497
818763A10
818763A11
818763A4
818763T11
9-72602
18-3751
21120
35912
445-226
509035
52834
775419
79448
8M0168577
8M2000347
8M2011027
9-72155
11380
18-2299
445-224
52833
79447
9-72641