Sierra 18-3752
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Within 30 days
Sierra 18-3752 Product Description
Essential Reliability for Your Outboard Engine
Keeping your Mercury outboard running smoothly starts with the right components securing critical moving parts. The Sierra 18-3752 stands out as a precision-engineered crankshaft retaining nut designed specifically for the driveshaft assembly. Crafted from high-strength materials, it provides the torque-holding power needed to withstand the rigors of marine environments, from choppy saltwater runs to long freshwater hauls.
Unlike standard nuts, this high-strength version resists loosening under vibration and high RPMs, preventing catastrophic failures that could leave you stranded. Boat owners swear by its durability, often reporting years of trouble-free performance even in demanding conditions.
Perfect Fit for Popular Mercury Models
This retaining nut is a direct replacement for OEM parts in a wide range of Mercury and Mariner 2-stroke outboards. It's commonly used in 45 to 125 HP three-cylinder engines, ensuring seamless integration without modifications. Key compatible models include:
- Mercury 45-50 HP (various years)
- Mariner 60-90 HP inline models
- Force outboards in the 70-120 HP range
- Chrysler marine engines sharing the same powerhead design
Always cross-reference your engine's serial number for the best match, as slight variations exist across production runs. This part restores factory-spec tension, maintaining optimal alignment between the crankshaft and driveshaft.
Simple Installation for DIY Mechanics
Swapping out a worn retaining nut doesn't require a full teardown. With basic tools like a torque wrench, impact driver, and thread locker, you can complete the job in under an hour:
- Secure the engine on a stable stand and remove the flywheel or lower cowling as needed.
- Apply penetrating oil to the old nut if seized, then carefully loosen with proper socket size.
- Clean threads thoroughly to ensure a snug fit.
- Thread on the new Sierra 18-3752 nut, applying blue Loctite for extra security.
- Torque to manufacturer specs—typically 40-50 ft-lbs—then recheck after a test run.
Pro tip: Inspect the driveshaft key and washer during replacement to catch wear early, extending the life of your lower unit.
Why Upgrade to High-Strength Construction
In marine applications, vibration and corrosion are the enemies of fasteners. The Sierra 18-3752's high-strength alloy fights back, offering superior tensile strength over generic hardware store alternatives. It locks down the driveshaft with unyielding grip, reducing play that leads to gear whine or premature bearing wear.
Owners of fishing boats and ski vessels report fewer mid-season breakdowns, attributing it to this nut's ability to maintain precise crankshaft positioning. It's not just a part—it's peace of mind on the water.
Long-Term Maintenance for Peak Performance
To maximize lifespan, integrate checks into your annual service routine. Look for thread galling, looseness, or corrosion during oil changes. Pair it with fresh gear lube and impeller inspections for a bulletproof powerhead.
If you're trailering frequently, double-check torque after each trip. This proactive approach keeps small parts from becoming big problems, saving you from costly shop visits.
Frequently Asked Questions
What engines is the Sierra 18-3752 compatible with?
It's designed for Mercury and Mariner 2-stroke outboards from 45-125 HP, especially three-cylinder models. Confirm with your serial number for exact fit.
Is the Sierra 18-3752 a direct OEM replacement?
Yes, it matches OEM specifications in size, strength, and threading, making it a plug-and-play swap for most compatible Mercury driveshafts.
What torque specs should I use for installation?
Refer to your service manual, but it's generally 40-50 ft-lbs. Always use thread locker and re-torque after initial run-in.
Why choose high-strength over standard nuts?
High-strength materials resist vibration loosening and corrosion better, crucial for marine use where standard nuts often fail prematurely.
How do I know if my retaining nut needs replacing?
Signs include unusual gear noise, driveshaft play, or visible thread damage. Replace during lower unit service if over five years old.
Can I use this on 4-stroke Mercury engines?
Primarily for select 2-strokes; check compatibility as 4-strokes often use different powerhead designs.
Does it come with any additional hardware?
It's a single retaining nut; inspect and reuse or replace washers and keys as needed during install.
Save $7 when you buy the Sierra 18-3752 for only $27 from NVN Marine! Same day shipping before 3pm.
Sierra 18-3752 Technical Specifications
| Type: | |
|---|---|
| Vendor: |
Sierra Engine Parts |
| Weight: |
0.25 lb |
Sierra 18-3752 User Reviews
Sierra 18-3752 Shipping & Return
| Shipping Weight: |
0.25 lb |
|---|---|
| Box Sizes: |
1.00 (h) x 6.00 (w) x 7.00 (l) |
| Cubic Feet: |
42.0 |
| Returnable: |
Yes |
For detailed shipping policy please check our Shipping Policy and you can find our Return and Refund Policy here.