Mercury 50 HP Oil & Filter Change
Fresh oil and a new filter are the cheapest insurance for your 50 hp Mercury 50 HP. Below is the oil filter we recommend, which 50 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 50 HP
Changing Oil On a Boat Motor – Mercury maintenance 40hp 50hp 60hp (oil/gear lube)
Tools Needed
- 18mm wrench
- Oil filter wrench or channel locks
- Rags
- Drain pan
- Funnel
- Gloves
Safety
- Make sure the motor is level before checking oil levels.
- Be careful when using channel locks to avoid damaging the oil filter.
Steps
- Pull the lever to release and remove the cover from the top of the motor.
- Remove the drain plug using an 18mm wrench, tilting the motor to the left to drain the oil.
- Clean the area around the drain plug and inspect the seal before reinstalling.
- Remove the oil filter, placing a rag underneath to catch any remaining oil.
- Lubricate the new oil filter with oil, ensuring it is coated evenly.
- Install the new oil filter by hand, turning it about half a turn, then using a filter wrench or channel locks for an additional quarter to half turn.
- Reinstall the drain plug, ensuring it is snug but not overtightened.
- Fill the motor with oil, using a funnel for larger containers, and check the level with the dipstick.
- Remove the two screws and plug on the opposite side of the oil block to access the gear lube.
- Inspect the seals on the screws and plug, replacing if necessary, and fill with gear lube 90.
Tips
- Turning the motor to the left while draining helps to ensure all the oil is removed.
- Using gloves when handling the gear lube screws and plug can help prevent a mess.
- Make sure to check the oil level with the motor level to get an accurate reading.
Which part do I need for my Mercury 50 HP?
For most 50 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) | 50 FourStroke, BigFoot, 50 FourStroke, Carb, BigFoot, 996cc, 50 FourStroke, Carb, Standard, 996cc and 40 more rigging variants | Find on Amazon → |
| 358M0065104 | Mercury OEM 358M0065104 (replaces Sierra 18-7914) | 50 FourStroke, BigFoot, 50 FourStroke, Carb, BigFoot, 996cc, 50 FourStroke, Carb, Standard, 996cc and 40 more rigging variants | Find on Amazon → |
| 8M0065103 | Mercury OEM 8M0065103 (replaces Sierra 18-7914) | 50 FourStroke, BigFoot, 50 FourStroke, Carb, BigFoot, 996cc, 50 FourStroke, Carb, Standard, 996cc and 40 more rigging variants | Find on Amazon → |
| 8M0065104 | Mercury OEM 8M0065104 (replaces Sierra 18-7914) | 50 FourStroke, BigFoot, 50 FourStroke, Carb, BigFoot, 996cc, 50 FourStroke, Carb, Standard, 996cc and 40 more rigging variants | Find on Amazon → |
| 8M0162829 | Mercury OEM 8M0162829 (replaces Sierra 18-7914) | 50 FourStroke, BigFoot, 50 FourStroke, Carb, BigFoot, 996cc, 50 FourStroke, Carb, Standard, 996cc and 40 more rigging variants | Find on Amazon → |
| 8M0162830 | Mercury OEM 8M0162830 (replaces Sierra 18-7914) | 50 FourStroke, BigFoot, 50 FourStroke, Carb, BigFoot, 996cc, 50 FourStroke, Carb, Standard, 996cc and 40 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 50 HP (50 hp)?
The Mercury 50 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 50 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 50 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 50 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 50 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 75 HP oil filter
- Mercury 25 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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