Drain Screw E-TEC | Sierra 18-4255

Sierra 18-4255 Drain Screw | Evinrude E-TEC Outboard Lower Unit

The Sierra #18-4255 is a replacement drain screw for Evinrude E-TEC outboard lower units. Replaces the lower unit drain or fill screw on E-TEC outboards when the original is lost, damaged, or has stripped threads. Confirm fitment against your E-TEC model's parts documentation before ordering.

Product Details:

• Part Number: 18-4255 (Sierra)
• SKU: SIERRA-18-4255
• Manufacturer: Sierra
• Type: Drain Screw
• Application: Evinrude E-TEC outboard lower unit
• Condition: New

Additional Information

Evinrude E-TEC — Lower Unit Drain and Fill Screws:

Evinrude E-TEC outboards use magnetic drain and fill screws in the lower unit gearcase. The magnetic drain screw collects ferrous metal particles suspended in the gear lube during operation — fine metal debris from normal gear and bearing wear accumulates on the magnet and is removed from circulation when the screw is inspected at gear lube service. Inspecting the drain screw magnet at each gear lube change is an important diagnostic step: a small amount of fine gray metallic fuzz on the magnet is normal; larger particles, chunks, or a significantly increased amount of debris warrants further gearcase inspection before returning to service.

When to Replace the Drain Screw:

The E-TEC lower unit drain screw should be replaced when:

• The screw is lost or missing — a missing drain screw will allow gear lube to drain completely from the gearcase, causing rapid gear and bearing failure if the outboard is operated
• The screw threads are stripped or damaged — a stripped screw cannot seal the drain port; gear lube loss will occur
• The gearcase housing drain port threads are damaged and a thread repair (Helicoil or similar) has been performed — a new screw is required for a clean thread engagement after any thread repair
• The screw head is damaged and cannot be removed with standard tools — replace rather than risk further damage to the housing bore

O-Ring Service at Screw Replacement:

The drain screw uses an O-ring or washer to seal the drain port. When replacing the drain screw, always install a new O-ring or washer. A new screw installed with a worn or previously compressed sealing element will not seal reliably. See Sierra 18-4253-9 (drain screw O-ring, pack of 5) for the compatible E-TEC drain screw sealing O-ring if your application uses O-ring sealing.

Drain Screw Magnet — Inspection at Service:

At each gear lube service, before reinstalling the drain screw:

• Wipe the magnet clean with a lint-free cloth and inspect the collected debris
• Fine gray metallic powder or a thin film of metallic fuzz is normal — this is expected wear from gear and bearing surfaces
• Larger metal flakes, chips, or an unusual increase in debris volume indicates abnormal wear — inspect the gearcase internally before refilling with fresh gear lube
• Bronze or brass-colored particles may indicate bearing cage wear — a more urgent inspection flag

Installation Notes:

• Confirm fitment against your E-TEC model's parts documentation before ordering
• Always install a new O-ring or sealing washer when replacing the drain screw
• Clean the drain port threads in the gearcase housing before installing the new screw
• Tighten to the torque specification in the Evinrude E-TEC service manual — do not overtighten into the aluminum gearcase housing
• Inspect drain screw magnet debris at every gear lube service as a gearcase health diagnostic

Frequently Asked Questions

1. Is the drain screw magnetic on E-TEC outboards?
Yes — the E-TEC lower unit drain screw is typically magnetic and collects ferrous metal particles from the gear lube during operation. Inspect the magnet at every gear lube change as a gearcase wear diagnostic.

2. What O-ring or washer does this screw use?
The drain screw requires a sealing O-ring or washer. See Sierra 18-4253-9 (drain screw O-ring, pack of 5) for the compatible O-ring if your E-TEC uses O-ring sealing. Always install a new sealing element when replacing the screw.

3. What happens if the drain screw is missing?
Gear lube drains from the gearcase through the open port. Operating the outboard with a missing drain screw causes the gearcase to run dry, leading to rapid gear and bearing failure. Install a replacement screw immediately.

4. What does metal debris on the drain screw magnet mean?
A small amount of fine gray metallic fuzz is normal. Large flakes, chips, or significantly increased debris indicates abnormal internal gearcase wear — inspect the gearcase before returning to service.

5. How tight should I torque the drain screw?
Refer to the torque specification in your Evinrude E-TEC service manual. Do not overtighten — the gearcase housing is aluminum and threads strip easily if the screw is overtorqued.