Mercury – Oil Tank Cap Assembly | DFI OptiMax 75–125HP | 36-8M0073266

Overview

Anyone who’s spent time with a 75–125HP OptiMax knows the oil tank cap isn’t something you think about—until it starts acting up. A cap that doesn’t seal right can let air sneak into the system, leave a light mist of oil under the cowl, or trip those random oil alarms that make you second-guess your whole day on the water. This OEM cap assembly replaces everything in one go: the cap, base, spacer, O-ring, tether, and the little hardware bits. Once it’s on, the tank seals properly again and the engine stops giving you attitude.

Key Features

 • Fits 75–125HP DFI OptiMax models – Covers engines in serial range 0T980000–2B123429.
 • All-in-One Kit – New cap, base, spacer, O-ring, nuts, and tether.
 • Snug, Clean Fit – Molded cap sits square and seals the tank neck the way it should.
 • Made for Real Marine Use – Handles heat, vibration, and oil vapor without warping.
 • OEM-Correct – Built to Mercury’s specs so the system stays airtight.

Engine & Boat Compatibility

 • Mercury 75HP OptiMax
 • Mercury 90HP OptiMax
 • Mercury 115HP OptiMax
 • Mercury 125HP OptiMax
 • Serial range 0T980000–2B123429

Performance & Practical Benefits

Putting on a fresh cap assembly usually clears up the little annoyances that creep in with age—oil mist, loose caps, and random beeps when nothing is actually wrong. A good seal keeps air out of the oil system, which helps the engine keep steady pressure, especially when the water gets rough. It’s a small part, but on these OptiMax motors, it makes a noticeable difference in how predictable the oiling system feels.

Why Buy OEM

OptiMax systems are touchy about air leaks. An aftermarket cap might look close, but “close” doesn’t cut it here. OEM caps sit right, clamp tight, and the O-ring material holds up to heat and oil fumes. It’s the difference between a system that behaves—and one that throws alarms for no good reason.

FAQ

Q1: What are the usual signs the oil cap assembly is shot?
A: Light oil residue, a cap that never feels tight, or random oil alarms at idle or cruise.

Q2: Does the kit come with everything I need?
A: Yep—cap, base, spacer, O-ring, tether, and nuts.

Q3: Can I swap it myself?
A: Most folks can. It’s a quick, easy job with basic tools.

Q4: Will this fix air getting into the oil system?
A: If the cap seal was the culprit, this usually solves it immediately.

Q5: Why choose OEM?
A: Better seal, better materials, and fewer mystery alarms—simple as that.