Mercury 25 HP Oil & Filter Change
Fresh oil and a new filter are the cheapest insurance for your 25 hp Mercury 25 HP. Below is the oil filter we recommend, which 25 HP variants it fits, a step-by-step video of the full oil change, and what else you need for the job.
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Watch: how to do it (step by step)
How to replace the oil filter on a Mercury 25 HP
How to change Mercury 25HP Outboard Oil
Tools Needed
- Oil filter wrench or special Mercury tool for oil filter removal
- Socket wrench (13mm)
- Funnel
- Gear lube pump (for gear oil change)
Safety
- Warm up the engine before starting to avoid burns
- Be careful when removing the oil filter to prevent spills
Steps
- Drain the old oil by loosening and removing the drain plug on the 25 Merc.
- Remove the oil filter using a special Mercury tool or an oil filter wrench.
- Lubricate the gasket of the new oil filter with some oil.
- Hand-tighten the new oil filter, then finish off with a wrench.
- Raise the motor to allow oil to drain back into the pan.
- Reinstall and snug the drain plug.
- Lower the unit and fill it with the recommended amount of oil (1 liter for this engine).
- Check the oil level using the dipstick.
- For gear oil change, remove the vent screw, pump in gear lube until it comes out of the top screw, then replace the vent screw.
Tips
- Ensure the motor is level when filling with oil to avoid measurement errors
- The oil may read slightly high initially but will work its way into all cracks after riding
Which part do I need for my Mercury 25 HP?
For most 25 HP owners the part above (18-7913) 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 (15)
| Part number | Description | Fits | |
|---|---|---|---|
| 18-7914 | OIL FILTER | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 35822626K03 | Mercury OEM 35822626K03 (replaces Sierra 18-7913) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 35822626Q03 | Mercury OEM 35822626Q03 (replaces Sierra 18-7913) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 35-822626Q04 | Oil filter | 25HP | Find on Amazon → |
| 35-822626Q1 | Mercury OEM 35-822626Q1 (replaces Sierra 18-7913) | 25HP | Find on Amazon → |
| 35-822626Q2 | Oil filter | 25HP | Find on Amazon → |
| 358M0065103 | Mercury OEM 358M0065103 (replaces Sierra 18-7914) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 358M0065104 | Mercury OEM 358M0065104 (replaces Sierra 18-7914) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 822626Q03 | Mercury OEM 822626Q03 (replaces Sierra 18-7913) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 8M0065103 | Mercury OEM 8M0065103 (replaces Sierra 18-7914) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 8M0065104 | Mercury OEM 8M0065104 (replaces Sierra 18-7914) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 8M0154778 | Mercury OEM 8M0154778 (replaces Sierra 18-7913) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 8M0162829 | Mercury OEM 8M0162829 (replaces Sierra 18-7914) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 8M0162830 | Mercury OEM 8M0162830 (replaces Sierra 18-7914) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | Find on Amazon → |
| 8M0162832 | Mercury OEM 8M0162832 (replaces Sierra 18-7913) | 25 FourStroke, Carb, 25 FourStroke, EFI, 25-20081 and 30 more rigging variants | 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 25 HP (25 hp)?
The Mercury 25 HP uses the oil filter sold as Sierra 18-7913, plus its OEM and aftermarket cross-references (15 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 25 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 25 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 25 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 25 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 90 HP oil filter
- Mercury 15 HP oil filter
- All Mercury maintenance guides
- Free Mercury boat valuation
- Buying a boat? Check whether the asking price is fair
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