Mercury 90 HP Oil & Filter Change
Fresh oil and a new filter are the cheapest insurance for your 90 hp Mercury 90 HP. Below is the oil filter we recommend, which 90 HP variants it fits, a step-by-step video of the full oil change, and what else you need for the job.
Check today’s price on Amazon →
Watch: how to do it (step by step)
How to replace the oil filter on a Mercury 90 HP
OIL CHANGE ON A 90 HP MERCURY OUTBOARD 4 STROKE EASY HOW TO ( MUST WATCH )
Tools Needed
- Ratchet with 10mm and 16mm sockets
- Channel locks
- Microfiber cloth
- Oil pump
- New oil filter
- New lower end seals
- 5.2 liters of 10W30 oil
Safety
- Wear rubber gloves to protect your hands.
- Be cautious of the oil and ensure it doesn't spill or damage surfaces.
Steps
- Run the engine with water for 10-15 minutes to heat up the fluids.
- Remove the engine cover and place it safely on the lawn.
- Remove the propeller by first loosening the bolt with a 10mm socket.
- Lower the motor using the trim on the side.
- Remove the bolt at the bottom of the motor with a 10mm socket.
- Allow the oil to drain for about an hour.
- Use channel locks to remove the oil filter.
- Install the new oil filter by applying a small amount of oil to the seal.
- Tighten the oil filter with a 16mm socket.
- Replace the lower end seals if they are damaged.
- Fill the lower end unit with quick silver marine lubricant using an oil pump.
- Tighten the drain plug and ensure oil is coming out.
- Reinstall the propeller and secure it with the bolt, using a 10mm socket.
- Add 5.2 liters of 10W30 oil to the motor.
- Replace the engine cover.
Tips
- Always check or replace the lower end seals to prevent water damage.
- Consider replacing the fuel filter and spark plugs according to the manufacturer's recommendations.
Which part do I need for my Mercury 90 HP?
For most 90 HP owners the part above (18-7914) is the right choice. Price tip: the aftermarket numbers are usually noticeably cheaper than the OEM-branded box — it is the same physical part. If you need an exact match, these compatible part numbers also fit:
Show all compatible part numbers (6)
| Part number | Description | Fits | |
|---|---|---|---|
| 358M0065103 | Mercury OEM 358M0065103 (replaces Sierra 18-7914) | 90, 90,900, 90HP | Find on Amazon → |
| 358M0065104 | Mercury OEM 358M0065104 (replaces Sierra 18-7914) | 90, 90,900, 90HP | Find on Amazon → |
| 8M0065103 | Mercury OEM 8M0065103 (replaces Sierra 18-7914) | 90, 90,900, 90HP | Find on Amazon → |
| 8M0065104 | Mercury OEM 8M0065104 (replaces Sierra 18-7914) | 90, 90,900, 90HP | Find on Amazon → |
| 8M0162829 | Mercury OEM 8M0162829 (replaces Sierra 18-7914) | 90, 90,900, 90HP | Find on Amazon → |
| 8M0162830 | Mercury OEM 8M0162830 (replaces Sierra 18-7914) | 90, 90,900, 90HP | Find on Amazon → |
Many of these are the same physical part under different brand numbers. Build years are shown where our parts data has them. Where a variant has no years, only the model code is listed. Confirm against your engine plate before ordering.
Frequently asked questions
What oil filter fits a Mercury 90 HP (90 hp)?
The Mercury 90 HP uses the oil filter sold as Sierra 18-7914, plus its OEM and aftermarket cross-references (6 compatible numbers are listed above). Confirm the number against your engine's model code and year plate before ordering.
How often should I replace the oil filter on a Mercury 90 HP?
Change the oil and filter every 100 running hours or once a season, whichever comes first (check your manual for the exact interval).
What else do I need for an oil change on a Mercury 90 HP?
The correct grade and amount of engine oil (see the manual or the video), a new drain-plug washer, a filter wrench and a drain pan or oil extractor pump. Nothing exotic — it is standard service equipment.
What are the signs the oil is overdue on a Mercury 90 HP?
Dark, gritty oil well past its interval, low-pressure warnings — and milky or grey oil, which means water is getting in and should be investigated immediately.
How long does an oil change take on a Mercury 90 HP?
About an hour for a competent DIYer. Run the engine warm first — warm oil drains faster and carries more contaminants out with it.
Related guides
- Mercury 50 HP oil filter
- Mercury 75 HP oil filter
- Mercury 25 HP oil filter
- Mercury 15 HP oil filter
- All Mercury maintenance guides
- Free Mercury boat valuation
As an Amazon Associate we earn from qualifying purchases — at no extra cost to you. Prices and availability are shown at checkout. This guide is for reference; always follow the engine manufacturer’s service manual.