Sierra 3070 Yamaha Impeller

The Sierra 3070 (18-3070) Impeller is a six-blade replacement lower-unit water pump impeller for select Yamaha two-stroke outboards. It rotates inside the water pump housing to draw cooling water through the gearcase and circulate it through the engine. Replaces Yamaha OEM impeller 688-44352-03-00. Included in Sierra water pump kits 18-3370 and 18-3371.

Parts Desk Insight Best Use

Note that 47-3070 can resemble a Mercury OEM impeller number but is the Land N Sea distributor SKU for Sierra 18-3070. Confirm that the Yamaha water pump diagram calls for 688-44352-03-00 before ordering especially on 6090 HP engines where Yamaha used several different pump designs across model years. The 688-series impeller spans a wide range of two-stroke models (19842009), so production year and full model code are both required for a reliable match.

Replace every 23 seasons or 200 hours regardless of visible wear. Sand, silt, dry operation, and extended storage can harden or damage the flexible blades, reducing cooling-water delivery before any visible external sign of failure.

Key Specifications

• Sierra part number: 18-3070
• Six flexible impeller blades
• Fits select Yamaha two-stroke 6090 HP outboards (19842009)
• Included in Sierra water pump kits 18-3370 and 18-3371
• Impeller only housing, wear plate, key, and seals not included
• UPC: 030999315229

Engine Compatibility

Documented Yamaha applications:

• 60 HP: 20042005
• 70 HP: 20042009
• C75: 19941999
• E75: 19952000
• P75: 19961999
• C80: 1997
• C85: 19911996
• CV85: 19891990
• 90 HP: 19842009
• 90 Jet: 19861989
• B90: 19971999
• C90: 19972001

Always confirm by complete engine model code, production year, serial number, and OEM water pump parts diagram showing 688-44352-03-00.

Alternate Part Numbers

• Sierra: 18-3070 / 118-3070
• Yamaha: 688-44352-03-00 / 688-44352-03
• GLM Marine: 89920
• Mallory Marine: 9-45603, 9-45603-10
• Aqua Power: 2006

Installation Notes

Lower-unit removal is required to access the water pump assembly. During service: inspect the pump housing, stainless cup, wear plate, key, and seals; remove any broken impeller fragments from cooling passages; lubricate the new impeller with clean soapy water or approved assembly lubricant; rotate the driveshaft in its normal operating direction while seating the housing over the blades. Confirm strong cooling-water telltale flow before operating under load. Never operate the outboard without an adequate cooling-water supply.

Compatible Yamaha Water Pump Kits

• Sierra 3371 Yamaha Water Pump Repair Kit
• Sierra 3433 Yamaha Water Pump Repair Kit
• Sierra 3434 Yamaha Water Pump Repair Kit
• Sierra 3442 Yamaha Water Pump Repair Kit

Related Yamaha Impellers

• Sierra 3071 (18-3071) Yamaha Impeller 115250HP
• Sierra 3042 (18-3042) Yamaha Impeller F75/F80/F90/F100
• Sierra 3074 (18-3074) Yamaha/Mercury/Mariner Impeller 9.915HP
• Sierra 3073 (18-3073) Yamaha/Mercury/Mariner Impeller 45HP
• Sierra Impeller 18-3086 Yamaha Outboard Water Pump Replacement

Always confirm fitment against your Yamaha service manual and full model/year before ordering.