Sierra 18-3068 Yamaha Impeller
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The Sierra 18-3068 is a six-blade replacement lower-unit water pump impeller for select Yamaha outboards. It installs inside the gearcase water pump and draws cooling water through the lower unit for circulation through the engine. The 47-3068 number is the Land 'N' Sea distributor SKU for Sierra part 18-3068. It replaces Yamaha impeller numbers 6H4-44352-00-00, 6H4-44352-01-00 and 6H4-44352-02-00.
Key Features
- Sierra manufacturer part number: 18-3068
- Distributor SKU: 47-3068
- Six flexible impeller blades
- Designed for select Yamaha outboards
- Replaces Yamaha 6H4-44352-00-00, 6H4-44352-01-00 and 6H4-44352-02-00
- Used in Sierra water pump kits 18-3408, 18-3413, 18-3429, 18-3430, 18-3432, 18-3440 and 18-3490
- Impeller only; housing, wear plate, key, seals and gaskets are not included unless separately specified
- UPC: 030999315205
Engine Compatibility
The strongest documented fitment is for select Yamaha 30, 40 and 50 HP outboards using an original 6H4-series water pump impeller. Additional catalogue references associate the impeller with certain Yamaha two-stroke and four-stroke applications from approximately 25 through 60 HP, but exact fitment depends on the engine model, year and gearcase configuration.
Serial Number Fitment Notice
Do not select this impeller by horsepower alone. Yamaha used more than one water pump configuration across engines carrying similar horsepower ratings.
Before ordering, confirm:
- Complete Yamaha engine model number
- Production year and serial number
- Gearcase and water pump assembly
- Original impeller number
- Yamaha reference 6H4-44352-00-00, 6H4-44352-01-00 or 6H4-44352-02-00
- Impeller bore and drive-key arrangement
The original Yamaha water pump diagram provides the most reliable fitment confirmation.
When This Part Needs Replacement
Replace the impeller if:
- Cooling-water discharge becomes weak or intermittent
- The engine begins running hotter than normal
- An overheat warning activates
- The blades are cracked, torn, stiff or permanently bent
- Rubber fragments are missing
- The centre hub slips inside the impeller
- The engine has been operated without cooling water
- The motor has operated regularly in sandy or silty water
- The scheduled water pump service interval has been reached
A worn impeller may still rotate while no longer moving enough water to cool the engine safely.
Installation Notes
Lower-unit removal is normally required to access the water pump assembly. During service:
- Disconnect the ignition and battery where applicable
- Follow the correct lower-unit and shift-linkage removal procedure
- Inspect the pump housing, stainless cup, wear plate, key, seals and driveshaft
- Remove broken impeller fragments from the pump and cooling passages
- Lubricate the new impeller with clean soapy water or an approved assembly lubricant
- Position the drive key correctly
- Rotate the driveshaft in its normal operating direction while lowering the housing over the blades
- Replace worn gaskets, O-rings and pump components
- Reinstall the lower unit according to the Yamaha service manual
- Confirm strong cooling-water flow before operating under load
Never operate the outboard without an adequate cooling-water supply.
Alternate/Superseded Part Numbers
- Sierra: 18-3068
- Land 'N' Sea distributor SKU: 47-3068
- Sierra catalogue reference: 118-3068
- Yamaha: 6H4-44352-00-00
- Yamaha: 6H4-44352-01-00
- Yamaha: 6H4-44352-02-00
- GLM Marine: 89900
- Mallory Marine: 9-45601
- Mallory Marine: 9-45601-10
- Aqua Power: 2009
- UPC: 030999315205
Parts Desk Insight
The 47-3068 number is a distributor stock number, not the Yamaha OEM number. Confirm that the engine's water pump diagram calls for one of the 6H4-44352 impeller numbers before ordering, particularly on 30–60 HP Yamaha outboards where several gearcase and pump configurations may be encountered.
Compatible & Related Products
Other Sierra Yamaha impellers and water pump kits available at Marisol Marine:
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.