Lower Unit Oil Drain Plug Screw Kit, 2 Screws with Gaskets – Fits Mercury/MerCruiser Outboard & Sterndrive Applications

Product Details

This Lower Unit Oil Drain Plug Screw Kit includes two non-magnetic drain/fill screws and two matching yellow gaskets for compatible marine gearcases. It is intended for Mercury/MerCruiser applications that use a 3/8-16 drain or fill screw, including selected Alpha One, Gen I, Gen II, I, R, MR, TR, and TRS sterndrive applications.

The kit is also intended for compatible Mercury outboards and selected Johnson/Evinrude and Chrysler/Force/US Marine outboards that use a 3/8-16 non-magnetic drain plug screw. Confirm the thread size, plug style, and application before ordering.

• Non-magnetic metal screws for compatible marine drain and fill applications.
• 3/8-16 UNC thread for manual installation with a gasket seal.
• Complete kit includes two drain plug screws and two matching yellow gaskets.
• Aftermarket replacement kit; not an OEM component.

Part Number Matrix

The following numbers are listed as reference or replacement numbers for compatible applications. Always verify the original part and thread specification before installation.

Engine & Model Compatibility

Compatibility depends on the drain plug design and thread specification. Check your engine or sterndrive service information and compare the original plug before ordering.

Mercury/MerCruiser: Intended for compatible outdrives and outboards using a 3/8-16 non-magnetic drain or fill screw. The Verado series is excluded from the stated outboard application unless specifically confirmed for the individual model.

Johnson/Evinrude and Chrysler/Force/US Marine: Intended for compatible outboard models using a 3/8-16 non-magnetic drain plug screw.

Technical Specs

Product Type

Lower unit oil drain/fill plug screw kit

Installation

Manual thread-in with gasket seal

Material

Non-magnetic metal

Thread Size

3/8-16 UNC

Quantity Per Pack

2 drain plug screws and 2 matching gaskets

Color

Silver/metallic screws with yellow gaskets

Package Dimensions

3.82 × 2.68 × 0.43 inches (97 × 68 × 11 mm)

Application

Compatible gear lube drain or fill hole

What’s in the Box

• 2 x Non-magnetic drain plug screws
• 2 x Yellow drain plug gaskets

Installation Notes

1. Confirm that the replacement screws match the original thread, length, head style, and magnetic specification.
2. Remove the top vent plug first, then remove the bottom drain plug and allow the old gear oil to drain completely.
3. Using a suitable gear lube pump, fill from the bottom hole until new lubricant flows from the top vent hole.
4. Install the top vent plug first, then install the bottom drain plug with a new gasket to minimize oil loss.
5. Torque both plugs according to the engine or sterndrive manufacturer’s service instructions. Do not overtighten.

Troubleshooting & FAQ

Safety & Important Information

• Verify the original part, thread specification, dimensions, and application before purchase.
• Do not install a magnetic plug where a non-magnetic plug is specified.
• Use new gaskets and follow the manufacturer’s lubricant and torque procedures.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended when service procedures or fitment are uncertain.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered for dependable service in real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing with attention to materials and quality control.