Mercury Mariner Oil Injection Reservoir Cap Assembly - 36-43300A9
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The Mercury MerCruiser Quicksilver 36-43300A9 is a genuine Mercury Marine OEM oil injection cap assembly for select Mercury, Mariner, and SportJet 2-stroke oil injection reservoir systems. This cap assembly installs on the engine-mounted oil tank and combines the reservoir cap, sealing function, float/sender assembly, and warning-system leads used to monitor oil level. It is used where the Mercury parts diagram specifically calls for 43300A9 / 36-43300A9.
Key Features
- Genuine Mercury Marine factory OEM oil injection cap assembly.
- Mercury/MerCruiser part number: 36-43300A9.
- Manufacturer part number: 43300A9.
- Complete cap-style reservoir sender assembly for select 2-stroke oil injection systems.
- Includes molded oil tank cap with integrated float/sender components.
- Designed for the engine-mounted oil reservoir, not the remote boat-mounted supply tank unless the parts diagram specifies this cap.
- Electrical sender leads are commonly associated with the oil warning circuit, including ground and warning-module connection points.
- Used to help seal the oil reservoir and provide low-oil level warning input on compatible engines.
Engine Compatibility
Common where-used application groups include select Mercury and Mariner 2-stroke / 2-cycle outboards and SportJet applications by serial number and oil injection system configuration, including:
- 105 HP, 140 HP, 210 HP, and 240 HP SportJet applications where specified
- Select 135 HP, 150 HP, 175 HP, 200 HP, 225 HP, and 250 HP V6 outboard applications where specified
- Select EFI, Black Max, XR2, XR4, XR6, Pro Max, SeaPro, Marathon, and performance V6 oil injection layouts where specified
- Engine-mounted 2-stroke oil reservoir assemblies using cap assembly 43300A9
Use this cap assembly only where the Mercury/Mariner parts diagram calls for 36-43300A9 / 43300A9.
Serial Number Fitment Notice
Confirm fitment by engine serial number, oil injection reservoir style, warning-module wiring, and exact Mercury oil tank diagram before ordering. Mercury used different oil tank caps, float senders, remote tank caps, and warning harness layouts across similar 2-stroke engines, so matching the cap by horsepower alone is not enough.
When This Part Needs Replacement
Replace this cap assembly if the oil reservoir cap is cracked, leaking, loose, no longer sealing properly, or if the float/sender circuit is causing false low-oil warnings after the reservoir and wiring have been inspected. It should also be replaced if the wiring is brittle, damaged, oil-soaked, corroded, or if the internal float mechanism no longer moves freely with the oil level.
Installation Notes
Install this cap only on the reservoir and diagram location that call for 36-43300A9 / 43300A9. Inspect the oil tank threads, sealing surface, wiring connectors, warning module leads, and reservoir condition before installation. After replacement, verify the cap seals correctly, the harness is routed away from heat and moving linkages, and the low-oil warning circuit operates according to the Mercury service manual for the specific engine.
Alternate/Superseded Part Numbers
- 36-43300A9 — Mercury/MerCruiser formatted part number
- 43300A9 — Manufacturer part number
- 43300A1 — earlier cap assembly reference to verify by serial number and diagram
- 43300A5 — earlier cap assembly reference to verify by serial number and diagram
- 43300A6 — earlier cap assembly reference to verify by serial number and diagram
- 99024A4 — earlier oil cap/sender reference to verify by serial number and diagram
Parts Desk Insight
Oil injection cap assemblies should be matched by reservoir style and warning-system wiring, not just by engine horsepower. A leaking cap, failed float, or incorrect sender can create low-oil alarms or oil-feed concerns, so the tank, cap seal, wiring, and warning module should be checked together before returning the engine to service.
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Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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