If you run a Mercury Super Speedmaster gearcase, you already know the prop hardware is not “generic.” The Mercury Racing OEM Prop Nut Washer Kit from Buckshot Racing #77 is built for Mercury Super Speedmaster—commonly referred to as Mark 4, Mark 6, SSM #4, and SSM #6.
These racing gearcases use dedicated prop hardware designed to seat correctly, lock securely, and survive the high RPM and load changes seen in competition outboard racing.
This kit includes the key components most racers replace during prop changes and gearcase service: the Chamfered Flat Washer 12-39698, the Splined Washer 12-39701, and the Brass Prop Nut 11-827614.
What’s included in the kit (and what each part does)
The 12-39698 chamfered flat washer is designed to seat cleanly and distribute load where the prop hardware clamps, helping maintain proper contact and reducing the chance of uneven seating.
The 12-39701 splined washer provides positive engagement where splines are required to help resist rotation and maintain a secure stack under acceleration and deceleration loads.
The system is finished with the 11-827614 brass prop nut, a common choice in racing hardware because it tightens smoothly and holds well under repeated service cycles.
Together, 12-39698, 12-39701, and 11-827614 create the correct prop nut washer stack for Mercury Super Speedmaster SSM #4 / SSM #6 applications.
Designed for Mercury Racing Super Speedmaster gearcases
The Super Speedmaster family is a purpose-built racing lower unit, and the prop hardware must match the gearcase. This washer-and-nut stack is intended specifically for gearcases commonly identified in racing circles as “Mark 4,” “Mark 6,” “SSM #4,” and “SSM #6” all referring to the same gearcase family groups.
Competition outboards where these gearcases are commonly found
The SSM #4 and SSM #6 gearcases are widely associated with classic and modern competition outboard racing classes and model names.
You’ll commonly see them referenced on Mercury Racing F1, S300, SST-120, SST-140, SST-200, and F1H2O applications, as well as series and naming such as USF1, F200, and F150.
They’re also commonly tied to Mercury’s high-output race outboards such as APX 200, APX 260, and APEX 360 competition racing outboards, where correct prop hardware stack-up is essential for safety and repeatable performance.
Why replacing prop hardware matters on SSM racing gearcases
On an SSM lower unit, prop changes are frequent and the loads are intense. Worn, mismatched, or damaged washers can prevent proper seating, while questionable nuts can compromise clamping force. Replacing the prop nut and washer stack with the correct components helps protect the propshaft threads, improves consistency during prop swaps, and supports reliable retention under race conditions.
Part number reference (for ordering and cross-checking)
This kit is made up of the following Mercury / Mercury Racing OEM prop hardware part numbers:
Chamfered Flat Washer: 12-39698
Splined Washer: 12-39701
Brass Prop Nut: 11-827614
Contact mike@buckshotracing77.com or +1-714-697-1716 with any questions.