Mercury 75 HP Water Pump Impeller Replacement
A worn impeller on your 75 hp Mercury 75 HP starves the engine of cooling water and can overheat it in minutes. Below is the water-pump kit we recommend, which 75 HP variants it fits, a step-by-step video, and the parts you need to do the job yourself.
Check today’s price on Amazon →
Watch: how to replace it (step by step)
How to replace the water pump impeller on a Mercury 75 HP
Mercury 75-115 Water Pump/ Impeller Replacement
Tools Needed
- Screwdriver
- Ratchet or impact wrench
- Grease (Mercury 24c)
Safety
- Ensure engine and surrounding area are cool before starting work.
- Be cautious when handling sharp edges.
Steps
- Remove the water pickup adapter, keeping its orientation.
- Carefully remove the old seal using a screwdriver.
- Take note of the water tube's orientation on the midsection.
- Remove the four 10mm bolts securing the impeller housing.
- Slide the housing up and off the drive shaft.
- Push down with a screwdriver to ease out the worn impeller.
- Inspect the new impeller; fins should stick straight out.
- Clean the mating surface of the midsection.
- Place the new gasket, ensuring holes line up correctly.
- Position the new plate with the slit facing the right direction.
- Apply grease liberally to the new impeller and key.
- Line up the impeller's keyhole with the drive shaft's key.
- Turn the drive shaft clockwise while pushing the housing counterclockwise to seat the impeller.
- Align the gaskets and start one bolt to help line up the others.
- Tighten the bolts in a crisscross pattern, avoiding over-tightening.
Tips
- Keep parts oriented correctly for easy reassembly.
- Use grease to aid installation and protect the new impeller during startup.
- Turn the drive shaft clockwise while pushing the housing counterclockwise to ensure proper impeller seating.
Which part do I need for my Mercury 75 HP?
For most 75 HP owners the part above (89630) 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 (42)
| Part number | Description | Fits | |
|---|---|---|---|
| 12043 | Impeller Kit | 75 FourStroke, 1731cc, 75 HP (3-cyl.), 75/80 FourStroke, 2.1L | cross-reference only |
| 12094 | Impeller Kit | 75 FourStroke, 1596cc, 75 FourStroke, 1731cc, 75 HP (3-cyl.) | cross-reference only |
| 12122 | Impeller | 75 (7.5 hp) | cross-reference only |
| 12161 | Water Pump Service Kit | 75/80 FourStroke, 2.1L | cross-reference only |
| 12280 | Impeller Kit | 75 HP (4-cyl.) | cross-reference only |
| 12290 | Impeller Kit | 75 HP (4-cyl.) | cross-reference only |
| 12409 | Water Pump Upper Housing | 75/80 FourStroke, 2.1L | cross-reference only |
| 12410 | Water Pump Upper Housing | 75 HP (4-cyl.) | cross-reference only |
| 18-1346 | For: 3.5-9.8 HP & Mercruiser, For: 75-125 3 & 4 cyl. belt driven water pump | 75 | Find on Amazon → |
| 18-3017 | Impeller / water-pump component | 75 | Find on Amazon → |
| 18-3056 | Impeller / water-pump component | 75 | Find on Amazon → |
| 18-3114 | Sierra 18-3114 | 75 | Find on Amazon → |
| 18-3116 | 3.780", 3.175", 3", 2.5" | 75 | Find on Amazon → |
| 18-3117 | Sierra 18-3117 | 75 | Find on Amazon → |
| 18-3122 | (Part of 18-3116 Housing) For: Alpha I – Generation 2 (Part of 18-3116 Housing) For: #1 Units thru S/N D494568 S/N D494569 & Above | 75 | Find on Amazon → |
| 18-3200 | For: 75-90 HP | 75 | Find on Amazon → |
| 18-3214 | Impeller for Honda BF75A | 75 | Find on Amazon → |
| 18-3217 | Sierra 18-3217 | 75 | Find on Amazon → |
| 18-3414 | Sierra 18-3414 | 75 | Find on Amazon → |
| 18-3436 | Sierra 18-3436 | 75 | Find on Amazon → |
| 30-43011 | Mercury OEM 30-43011 (replaces Sierra 18-1346) | 75 | Find on Amazon → |
| 30-43011T | Mercury OEM 30-43011T (replaces Sierra 18-1346) | 75 | Find on Amazon → |
| 324351 | Mercury OEM 324351 (replaces Sierra 18-3117) | 75 | Find on Amazon → |
| 41316 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 43024A7 | Mercury OEM 43024A7 (replaces Sierra 18-3214) | 75 | Find on Amazon → |
| 478M0100526 | Mercury OEM 478M0100526 (replaces Sierra 18-3214) | 75 | Find on Amazon → |
| 48752T | Mercury OEM 48752T (replaces Sierra 18-3114) | 75 | Find on Amazon → |
| 52269 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 70502 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 71360 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 80288 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 80580 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 8172761 | Mercury OEM 8172761 (replaces Sierra 18-3122) | 75 | Find on Amazon → |
| 89810 | Water Pump Upper Housing | 75 (7.5 hp) | cross-reference only |
| 89840 | Water Pump Upper Housing | 75 HP (4-cyl.) | cross-reference only |
| 8M0100526 | Mercury OEM 8M0100526 (replaces Sierra 18-3214) | 75 | Find on Amazon → |
| 8M0204677 | Mercury OEM 8M0204677 (replaces Sierra 18-3117) | 75 | Find on Amazon → |
| 8M0204709 | Mercury OEM 8M0204709 (replaces Sierra 18-3122) | 75 | Find on Amazon → |
| 90794 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 92192 | Water Pump Service Kit | 75 (7.5 hp) | cross-reference only |
| 96146A5 | Mercury OEM 96146A5 (replaces Sierra 18-3414) | 75 | Find on Amazon → |
| 96148T1 | Mercury OEM 96148T1 (replaces Sierra 18-3116) | 75 | 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 water pump impeller fits a Mercury 75 HP (75 hp)?
The Mercury 75 HP uses the impeller sold as Sierra 18-1346, plus its OEM and aftermarket cross-references (42 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 impeller on a Mercury 75 HP?
Replace the water pump impeller every 1-3 years or roughly every 200-300 running hours, whichever comes first — and sooner if you run in silty, sandy or shallow water.
What are the symptoms of a failing impeller on a Mercury 75 HP?
A weak or missing telltale stream, engine temperature climbing above normal, or an overheat alarm are the classic warning signs. A worn impeller can overheat and damage the engine within minutes, so don't delay the job.
Do I need the full water pump kit or just the impeller?
For the 75 HP, fit the complete kit. The seals, O-rings, gasket and wear plate age alongside the impeller, and replacing them together is the reliable, do-it-once job.
How long does a water pump job take on a Mercury 75 HP?
For a competent DIYer it's typically a 1-2 hour job of medium difficulty. The step-by-step video above covers every step.
Related guides
- Mercury 60 HP water pump / impeller
- Mercury 70 HP water pump / impeller
- Mercury 115 HP water pump / impeller
- Mercury 90 HP water pump / impeller
- All Mercury water pump 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.