Sierra 18-3730 Nut Lock-OMC Cobra & Volvo SX
Shipping (3PM)
Within 30 days
Sierra 18-3730 Nut Lock-OMC Cobra & Volvo SX Product Description
Secure Your Sterndrive with Confidence
Nothing disrupts a day on the water like a loose propeller, and that's where a dependable nut lock steps in. Designed specifically for OMC Cobra and Volvo SX sterndrives, this component grips the propeller nut firmly, countering the relentless vibration and torque from high-speed operation. Boat owners know the frustration of saltwater exposure weakening standard fasteners—replacing with a precision-engineered nut lock restores that peace of mind, ensuring your drive train stays locked tight through rough wakes and long hauls.
Marine enthusiasts often overlook these small parts until they fail, but proactive swaps during routine servicing can prevent catastrophic spin-offs. It's not just about holding on; it's about extending the life of your investment in choppy bays or open ocean runs.
Perfect Fit for Your Setup
This nut lock aligns seamlessly with a range of OMC Cobra models, including popular Stringer and Viking variants, as well as Volvo Penta SX drives. Whether you're running a classic Cobra from the '80s or a later SX setup, it mates perfectly with the factory-spec propeller nuts, eliminating wobble or slippage that plagues worn originals.
- OMC Cobra sterndrives (various ratios and serial ranges)
- Volvo Penta SX outdrives (standard and DuoProp configurations)
- Compatible with both single and dual-prop applications
Before installing, double-check your drive serial number against OMC or Volvo references—it's a quick step that saves headaches. This isn't a one-size-fits-all; it's tailored for these workhorses of the water.
Built to Withstand the Elements
Crafted from durable materials that resist corrosion from brine and freshwater alike, this nut lock maintains its bite even after seasons of exposure. Unlike generic hardware store fixes that deform or rust out quickly, it features a specialized design that deforms just enough to lock in place without galling the nut threads.
- High-tensile strength to handle prop thrust
- Precision dimensions for OEM-level fit
- Anti-vibration locking mechanism
- Easy to source as a direct aftermarket upgrade
Boaters in coastal areas swear by these for their reliability—think of it as the unsung hero that keeps your prop from walking off mid-run.
Simple Swap for Weekend Warriors
Installing a new nut lock takes minutes with basic tools: a prop wrench, torque wrench, and anti-seize compound. Start by removing the old prop and nut, clean the shaft thoroughly, slide on the new lock, thread the nut, and torque to manufacturer specs (typically around 50-75 ft-lbs, but verify your manual). The lock's insert grabs immediately, providing instant security.
Pro tip: Inspect the shaft splines and keyway while you're in there—worn ones amplify loosening risks. Fresh gear lube on the shaft reduces future drag and makes props easier to service next time.
- Secure boat on trailer or lift
- Remove cotter pin and castle nut
- Extract prop and discard old lock
- Install new lock and nut
- Torque, pin, and test spin
Many skip this during oil changes, but it's a 10-minute job that pays dividends in safety.
Long-Term Reliability Tips
To maximize lifespan, pair this nut lock with annual drive inspections. Look for thread wear or excessive play, which signal replacement time. In high-hour engines, upgrade to stainless props for even better synergy. Saltwater users, rinse your drive religiously—galvanic corrosion sneaks up fast on overlooked parts.
Real-world feedback from forums and marinas highlights how these hold up better than some OEM pieces, especially in abuse-prone setups like tow boats or fishing rigs pounding through swells.
Frequently Asked Questions
What is a nut lock and why do I need one for my OMC Cobra or Volvo SX?
A nut lock is a specialized washer or insert that prevents the propeller nut from loosening due to engine vibration and water forces. On OMC Cobra and Volvo SX sterndrives, it's essential for safety, as a loose prop can lead to loss of control or damage.
Which sterndrive models is the Sierra 18-3730 compatible with?
It's designed for OMC Cobra (Stringer, Viking series) and Volvo Penta SX drives, fitting most propeller nut setups from these lines. Confirm with your drive's serial for exact match.
How do I know if my current nut lock needs replacing?
Replace it if you see deformation, rust pitting, or if the prop nut spins easily by hand. Annual checks during servicing catch issues early.
Is installation DIY-friendly?
Yes, with a prop wrench and torque wrench. Clean the shaft, install the lock under the nut, torque properly, and secure with a cotter pin—no special skills required.
Can this nut lock handle saltwater use?
Absolutely—its corrosion-resistant construction stands up to marine environments. Rinse your drive after use to extend its life even further.
What's the difference between this and OEM parts?
Aftermarket versions like this offer identical fit and performance, often at better value, with proven durability in boater tests.
Should I replace the nut lock every time I service the prop?
It's recommended, as they wear with each removal and torque cycle. Proactive replacement prevents failures.
Does it work with dual-prop setups?
Yes, compatible with Volvo SX DuoProp configurations, ensuring secure hold on both props.
Save $1 when you buy the Sierra 18-3730 Nut Lock-OMC Cobra & Volvo SX for only $3 from NVN Marine! Same day shipping before 3pm.
Sierra 18-3730 Nut Lock-OMC Cobra & Volvo SX Technical Specifications
| Type: | |
|---|---|
| Vendor: |
Sierra Engine Parts |
| Weight: |
0.02 lb |
Sierra 18-3730 Nut Lock-OMC Cobra & Volvo SX User Reviews
Sierra 18-3730 Nut Lock-OMC Cobra & Volvo SX Shipping & Return
| Shipping Weight: |
0.02 lb |
|---|---|
| Box Sizes: |
0.00 (h) x 4.00 (w) x 5.00 (l) |
| Cubic Feet: |
0.0 |
| Returnable: |
Yes |
For detailed shipping policy please check our Shipping Policy and you can find our Return and Refund Policy here.