The Sierra 18-3721 Locknut is a replacement retaining, fastening or spacing component for the applicable assembly in Mercruiser applications. It replaces Mercruiser 8M0204653.
Material:Â Stainless Steel w/ nylon insert
Thread Size:Â 7/16" or 11.1mm - 20
For:Â MCM inner transom studs and prop nut for Mercury 39, 60 (1968 & newer, 8 spline)
For: Mouting Bravo drive bellhousings
Sold as a pack of 5
Need help with fitment? Contact us with your engine model and serial number and we'll help check suitability.
What is Sierra 18-3721?
Sierra 18-3721 is an aftermarket locknut for Mercruiser applications.
Which part numbers cross-reference Sierra 18-3721?
This listing cross-references Mercury 11-8M0204653, GLM 21170, Mercruiser 11-21298 and Mercruiser 11-22178. See the Cross References & Alternative Products section above for linked alternatives where available.
How can I check whether Sierra 18-3721 fits my Mercruiser application?
Contact us with your engine model and serial number and we'll help check suitability.
Australian Dollars
