Sierra 18-1236 Drain Screw, OEM 309243, for OMC Cobra V-6 40-50 HP Drives (1989-97)

The Sierra 18-1236 is a gearcase drain screw machined from alloy steel with a machined finish for corrosion resistance and a clean, precise fit. It is designed as a direct equivalent to OMC part 309243, used to seal the drain/fill port on the lower unit or drive housing during service. The screw uses a flat head with a Torx socket drive and a #6-40 fully-threaded, right-hand Unified National Coarse (UNC) shaft, compatible with a 0.25 inch groove diameter. Its compact 0.39 x 0.39 x 0.39 inch dimensions make it a small, easily overlooked but essential part to have on hand any time the gearcase is drained for an oil change or inspection.

This drain screw is intended for OMC Cobra drives and V-6 40-50 HP applications from 1989-97. A dedicated O-ring is used with the 18-1236 drain screw to complete the seal; the O-ring is a separate, individually sold component and is not included with this screw. Each unit is sold as a single drain screw.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-1236
• OEM Cross Reference: 309243
• Material: Alloy Steel
• Exterior Finish: Machined
• Head Style: Flat
• Drive System: Torx
• Thread Size: #6-40
• Thread Style: Right Hand
• Thread Coverage: Fully Threaded
• Set Screw Thread Type: Unified National Coarse (UNC)
• Item Dimensions: 0.39 x 0.39 x 0.39 inches
• Compatible Groove Diameter: 0.25 inches
• Number of Pieces: 1
• Weight: 0.01 pounds

Fitment

• OMC Cobra drives
• V-6 40-50 HP (1989-97)

Replaces (OEM)

• OMC 309243

Frequently Asked Questions

What does the Sierra 18-1236 drain screw fit? The Sierra 18-1236 drain screw is designed for OMC Cobra drives and V-6 40-50 HP applications from 1989-97.

What OEM part number does the 18-1236 replace? It is a direct equivalent to OMC part number 309243.

Is the 18-1236 a genuine Sierra part? Yes, 18-1236 is Sierra's own manufacturer part number for this drain screw, not a third-party knockoff.

What is the drain screw made of? The 18-1236 drain screw is machined from alloy steel with a machined finish for durability and corrosion resistance.

What thread size does the 18-1236 use? It has a #6-40 thread that is fully threaded, right-hand, and Unified National Coarse (UNC).

What drive type does the screw head use? The 18-1236 has a flat head with a Torx socket drive.

How big is the Sierra 18-1236 drain screw? It measures 0.39 x 0.39 x 0.39 inches and is compatible with a 0.25 inch groove diameter.

Does the 18-1236 come with an O-ring? No, the O-ring used with the 18-1236 drain screw is sold separately as its own part.

How much does the 18-1236 drain screw weigh? It weighs 0.01 pounds.

How many drain screws are included per order? Each Sierra 18-1236 order includes a single drain screw.

When would I need to replace this drain screw? The 18-1236 is typically replaced whenever the gearcase oil is drained and the screw or its O-ring shows wear, since a worn seal can allow oil to leak from the drive.