Mercury – Oil Cap Assembly | Engine Maintenance | Polyamide Resin | 8M0142290

Overview

Anyone who has spent time offshore knows that trust in your engine comes from the little things—those parts you rarely think about but rely on every single trip. The Mercury Oil Cap Assembly 8M0142290 is one of those simple but essential pieces that keeps everything buttoned up and running the way it should. When you twist this cap into place and feel it seat securely, there is a real sense of confidence there. It is one of those quiet reminders that your engine is protected, sealed, and ready for whatever the day brings—whether you are easing out before sunrise or making that long run back to the dock with the wind pushing behind you.

Key Features

• Designed for proper sealing and oil system protection on Mercury outboards
• Durable polyamide resin construction for longevity
• Includes cap with O-ring already installed for a ready-to-use fit
• Manufactured to Mercury Marine original equipment standards
• Engineered for tough marine environments, resisting heat and chemical exposure
• Mercury Marine part number 8M0142290

Engine & Boat Compatibility

• Fits Mercury 175–225 horsepower 3.4L V6 FourStroke outboards (serial number 2B529482 and up)
• Fits Mercury 200–300 horsepower 4.6L V8 FourStroke outboards (serial number 2B529482 and up)
• Fits Mercury 350–425 horsepower 5.7L V10 FourStroke outboards (serial number 3B266064 and up)
• Works with Mercury Racing 150R–500R V6, V8, and V10 outboards
• Ideal for center consoles, bay boats, performance hulls, pontoons, and freshwater fishing boats

Performance & Practical Benefits

An oil cap may be small, but on a modern outboard, it plays a bigger role than most folks realize. This cap threads on smoothly with a tight, steady feel, giving you that reassuring “click” of a proper seal. With the O-ring included and already installed, you avoid the usual fumbling or guessing that can happen with cheaper alternatives. Once in place, the cap resists vibration, heat, and splashing—conditions that would quickly wear down lesser materials.

Polyamide resin is chosen for a reason: it handles the constant expansion and contraction that comes from hot running days and cool night storage. It will not crack, glaze, or warp, even after seasons of hard use. That means fewer leaks, fewer worries, and a cleaner, more reliable engine compartment. The secure fit helps maintain the right internal pressure and oil retention, which directly contributes to smoother performance and longer engine life.

Why Buy OEM

When it comes to something as critical as your engine’s oil system, shortcuts simply are not worth it. An aftermarket cap might fit “close,” but close is not good enough when a poor seal can lead to leaks, contamination, or long-term wear. Mercury OEM parts are built from the correct materials, made to exact specifications, and tested against the same real-world extremes your engine faces every day.

Buying OEM is not just about matching a part number—it is about knowing that once the cap is on, the job is done right. No adjusting, no modifying, no nagging doubt. Just a proper seal, dependable performance, and peace of mind.

FAQ

Q1: Which Mercury engines does the 8M0142290 Oil Cap Assembly fit?

It fits Mercury 3.4L V6, 4.6L V8, and 5.7L V10 FourStroke outboards, as well as Mercury Racing V6, V8, and V10 models.

Q2: What makes this oil cap different from aftermarket versions?

OEM materials and exact engineering ensure a perfect seal, better durability, and proper long-term performance.

Q3: How do I confirm this is the correct replacement?

Match your engine model and serial number with the fitment list provided above.

Q4: Can it be used in both freshwater and saltwater?

Absolutely—its polyamide resin material is designed for all harsh marine conditions.

Q5: Is installation simple?

Yes. It threads on cleanly, with the O-ring pre-installed for quick, straightforward installation.