Mercury Marine/Mercruiser Water Pump Base Gasket – Fits 30-300 HP (Replaces 27-430331, 430331, 43033, Honda: 19234-ZW1-003)
Mercury Marine/Mercruiser Water Pump Base Gasket – Fits 30-300 HP (Replaces 27-430331, 430331, 43033, Honda: 19234-ZW1-003) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Free standard shipping on all orders under 1 KG
Mercury Marine/Mercruiser Water Pump Base Gasket – Fits 30-300 HP (...
Product Details
This is a replacement Water Pump Base Gasket designed for a wide array of Mercury Marine/Mercruiser outboard motors, generally fitting engines from 30 HP to 300 HP across various model years. It ensures a proper seal within the water pump assembly, which is critical for maintaining correct engine cooling and preventing overheating.
It serves as a direct interchange for Mercury Marine/Mercruiser part numbers 27-430331, 430331, and 43033, as well as Honda part 19234-ZW1-003.
- Installation Type: Impeller Gasket for Outboard Motors.
- Engine Protection: Creates a secure seal to prevent water leaks and maintain cooling system pressure.
- Guaranteed Fit: Engineered to meet or exceed the performance of the original equipment gasket.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury Marine/Mercruiser | 27-430331 |
| Mercury Marine/Mercruiser | 430331 |
| Mercury Marine/Mercruiser | 43033 |
| Honda | 19234-ZW1-003 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket fits a broad range of Mercury/Mariner outboards and Alpha One sterndrives. Please verify your engine's serial number falls within the ranges specified.
| Brand | Model | Rated HP | Stroke | Years / Serial Number | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 45 BODENSEE | 45 | 4-Stroke | 0G760300 THRU 0T178499, 0P017000 THRU 0P094499, 0G231123 THRU 0G760299, 9944807 THRU 0P016999 | 27-430331 | |
| Mercury | 45 JET | 45 | 0D000750 THRU 0G290584, 9683055 THRU 9885344, 0G290585 THRU 0G589999, 9885385 THRU 9973099, 0G760300 THRU 0T129554, 0P017000 THRU 0P094499, 0G590000 THRU 0G760299, 9973100 THRU 0P016999 | 27-430331 | ||
| Mercury | 50 | 50 | 3-Cylinder | 0D000750 THRU 0G290584, 9683055 THRU 9885344, 0G290585 THRU 0G589999, 9885345 THRU 9973099 | 27-430331 | |
| Mercury | 50 | 50 | 4-Stroke | 0G760300 THRU 0T178499, 0P017000 THRU 0P094499, 0G231123 THRU 0G760299, 9944807 THRU 0P016999 | 27-430331 | |
| Mercury | 50 | 50 | 4-Stroke (4 Cyl.) | 0P094500 THRU 0P206999, 0T178500 THRU 0T598999 | 27-430331 | |
| Mercury | 50 BIGFOOT | 50 | 4-Stroke | 0G760300 THRU 0T178499, 0P017000 THRU 0P094499, 0G231123 THRU 0G760299, 9944807 THRU 0P016999 | 27-430331 | |
| Mercury | 50 EFI | 50 | 4-Stroke (4 Cyl.) | 0P153500 THRU 0P400999, 0P401000 THRU 0P515896, 0T409000 THRU 1B344306, 1C000001 THRU 1C050251, 0P515897 & Up, 1C050252 & Up | 27-430331 | |
| Mercury | 55 | 55 | 3-Cylinder | 0D000750 THRU 0G290584, 9741042 THRU 9885344, 0G290585 THRU 0G589999, 9885345 THRU 9973099, 0P325500 & Up, 0T980000 & Up, 0G760300 THRU 0T979999, 0P017000 THRU 0P325499, 0G590000 THRU 0G760299, 9973100 THRU 0P016999 | 27-430331 | |
| Mercury | 60 | 60 | 3-Cylinder | 0D000750 THRU 0G290584, 9683055 THRU 9885344, 0G290585 THRU 0G589999, 9885345 THRU 9973099, 0P325500 & Up, 0T980000 & Up, 0G760300 THRU 0T979999, 0P017000 THRU 0P325499, 0G590000 THRU 0G760299, 9973100 THRU 0P016999 | 27-430331 | |
| Mercury | 60 BIGFOOT | 60 | 3-Cylinder | 0G760300 THRU 0T979999, 0P017000 THRU 0P325499, 0G590000 THRU 0G760299, 9973100 THRU 0P016999 | 27-430331 | |
| Mercury | 60 | 60 | 4-Stroke (4 Cyl.) | 0P094500 THRU 0P206999, 0T178500 THRU 0T598999 | 27-430331 | |
| Mercury | 60 EFI | 60 | 4-Stroke (4 Cyl.) | 0P153500 THRU 0P400999, 0P401000 THRU 0P515896, 0T409000 THRU 1B344306, 1C000001 THRU 1C050251, 0P515897 & Up, 1C050252 & Up | 27-430331 | |
| Mercury | 65 JET | 65 | 0D283222 THRU 0G760299, 0G760300 THRU 0T979999, 0P017000 THRU 0P325499, 9793577 THRU 0P016999 | 27-430331 | ||
| Mercury | 65 JET | 65 | 3-Cylinder | 0T980000 THRU 0T999999, 1B000001 & Up | 27-430331 | |
| Mercury | 65 JET | 65 | 4-Stroke | 2B095049 & Up | 27-430331 | |
| Mercury | 70 | 70 | 3-Cylinder | 0B240451 THRU 0C221999, 9506481 THRU 9589038 | 27-430331 | |
| Mercury | 75 | 75 | 3-Cylinder | 0B240451 THRU 0C221999, 9506481 THRU 9589038, 0C222000 THRU 0D283221, 9589039 THRU 9793576, 0D283222 THRU 0G760299, 0G760300 THRU 0T979999, 0P017000 THRU 0P325499, 0P325500 & Up, 0T980000 THRU 0T999999, 1B000000 & Up, 1B000001 & Up, 9793577 THRU 0P016999 | 27-430331 | |
| Mercury | 75 | 75 | 4-Stroke | 0G960500 THRU 0T800999, 0T801000 THRU 1B226999 | 27-430331 | |
| Mercury | 75 DFI | 75 | 3-Cylinder (1.5L) | 0T980000 THRU 1B226999, 1B227000 THRU 1B417701, 1B417702 THRU 1B736885, 1B736885 & Up | 27-430331 | |
| Mercury | 75 EFI | 75 | 4-Stroke | 1B172291 THRU 1B366822, 1B366823 THRU 2B094995, 2B095049 & Up | 27-430331 | |
| Mercury | ALPHA ONE | S/N 0D469859 THRU 0F679999 | 27-430331 | GEN. II | ||
| Mercury | ALPHA ONE | S/N 0F680000 THRU 0K999999 | 27-430331 | GEN. II | ||
| Mercury | ALPHA ONE | S/N 0L100040 & Up | 27-430331 | GEN. II |
Technical Specs
- Product Type
- Water Pump Base Gasket
- Installation
- Impeller Gasket for Outboard Motors
- Dimensions
- Height: 6.0 in; Width: 7.5 in; Length: 1.13 in
- Weight
- 0.014 kg (0.03 lb)
- Warranty
- 1 year factory warranty against defects and workmanship
What’s in the Box
- 1 x Gasket (Replaces 27-430331, 430331, 43033)
Installation Notes
- Disconnect the battery and ensure the engine is turned off and cool.
- Locate the lower unit of the outboard motor. You will likely need to remove it from the engine's midsection by undoing the main bolts.
- With the lower unit separated, locate the water pump housing, typically secured by four to six bolts.
- Carefully remove the bolts and lift the water pump housing off. The old impeller and gaskets will be visible.
- Remove the old water pump base gasket, ensuring the mating surface on the lower unit is completely clean of any old gasket material or sealant.
- Place the new base gasket onto the cleaned surface, ensuring it aligns with all bolt holes and water passages.
- Reassemble the water pump components (impeller, housing, etc.) in the reverse order of removal.
- Re-attach the lower unit to the engine, tighten all bolts to the manufacturer's specified torque, and reconnect the battery.
- Test the engine using a water supply (flushing muffs) to check for proper water flow and leaks.
Troubleshooting & FAQ
How do I know if my water pump gasket is failing?
Signs of a failing gasket include the engine overheating at idle or low speeds, a weak or inconsistent water stream from the "telltale" outlet, or visible water leaks around the seam of the water pump housing on the lower unit.
Is this gasket compatible with my engine if the stroke isn't listed?
Most likely, yes. This gasket fits a wide range of Mercury engines from 30-300 HP, covering 2-stroke, 4-stroke, DFI, and EFI models. The most reliable way to confirm fitment is to match your engine's model and serial number to our compatibility table or cross-reference the OEM part number 27-430331.
What is the recommended replacement interval?
It is best practice to replace the entire water pump impeller kit, including this base gasket, every 100-200 service hours or every 1-2 years, whichever comes first. This interval should be shortened if you operate frequently in saltwater or sandy/silty conditions.
Can I reuse my old gasket if it looks okay?
No. Gaskets are single-use components that compress to create a seal. Once the water pump housing has been removed, the old gasket will not provide a reliable seal and should always be replaced to prevent leaks and potential engine damage.
Does this replace the gasket for both plastic and metal water pump housings?
Yes, this gasket is designed to work with the standard water pump assemblies on the listed Mercury, Mariner, and Mercruiser Alpha One models, which may feature either plastic or metal top housings depending on the specific application and year.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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