Sierra 18-3081 Neoprene Impeller Kit | 12-Fin 12-Spline | Volvo Penta 3862281 / Johnson 09-1027B

Sierra 18-3081 Neoprene Impeller Kit

Part Number: 18-3081 (Sierra)  |  Catalog Number: 47-3081  |  Brand: Sierra

Sierra 18-3081 is a 12-fin neoprene flexible impeller kit for selected Volvo Penta, OMC, Johnson Pump, and Jabsco raw-water pump applications. It restores proper seawater circulation when the original impeller has become worn, hardened, cracked, or damaged.

The impeller uses a 12-spline brass hub and measures approximately 2.255 in. / 57.3 mm outside diameter and 1.243 in. / 31.6 mm wide. The 12-spline hub is a key fitment identifier — several other 12-blade impellers in the same diameter range use different hub configurations and are not interchangeable.

Specifications

• Manufacturer Part Number: 18-3081
• Catalog / Item Number: 47-3081
• Brand: Sierra
• Product Type: Flexible Impeller Kit
• Material: Neoprene
• Fins / Blades: 12
• Hub Drive: 12-spline brass
• Outside Diameter: approx. 2.255 in. / 57.3 mm
• Width: approx. 1.243 in. / 31.6 mm
• Bore: approx. 0.525 in. / 13.3 mm
• System: Marine engine raw-water (seawater) cooling pump
• UPC: 030999315335

Compatible Applications

Fitment is determined by the installed pump model or existing impeller number — not engine displacement alone. Confirmed cross-references:

• Volvo Penta 875811-2
• Volvo Penta 3858256
• Volvo Penta 3862281
• Volvo Penta 21951346
• Volvo Penta 24715100
• OMC 3858256
• Johnson Pump 09-1027B
• Johnson Pump 09-1027B-9
• Jabsco 1210-0001
• Jabsco 1210-0003
• Sierra 18-3586 raw-water pump applications
• GLM 89540
• Mallory 9-45703

This impeller is used across a broad range of Volvo Penta gasoline and diesel installations — AQ-series through 3.0L, 4.3L, 5.0L, 5.7L, 7.4L, 8.1L, and selected diesel applications — but the installed pump number is the most reliable fitment reference.

Fitment Notice

Before ordering, confirm all of the following:

• 12 fins / blades
• Hub drive: 12-spline (not keyed or single-flat)
• Outside diameter: approx. 2.255 in. / 57.3 mm
• Width: approx. 1.243 in. / 31.6 mm
• Original reference matches one of the cross-reference numbers above

Do not confuse this impeller with the wider Johnson Pump 09-812B / Jabsco 13554-0001 design — both have 12 blades and a splined hub but differ in width and pump application and are not interchangeable.

Some pump arrangements associated with Volvo Penta 3862281 use a three-bolt cover with a specific gasket. Confirm your pump’s cover and gasket configuration before disassembly and source the correct sealing components for your pump.

Service Interval

Inspect the impeller at each annual cooling-system service. Replace immediately when any of the following are observed:

• Reduced or absent raw-water flow at the exhaust outlet
• Engine running hotter than normal
• Pump slow to prime or fails to prime
• Blades cracked, torn, hardened, or permanently set
• Blade tips missing — inspect all downstream hoses, heat exchangers, and oil coolers before fitting the replacement
• Pump has operated dry (replace immediately)
• Service history is unknown
• Annual service interval or 500–1,000 operating hours reached, whichever comes first

Installation Notes

• Shut down the engine and disconnect the battery
• Close the raw-water intake seacock
• Note the pump cover and gasket arrangement before disassembly — the 3862281 pump family uses a specific three-bolt cover in some installations
• Remove the old impeller carefully without scoring the pump housing bore
• Inspect the cover plate, cam surface, shaft, and pump body for wear or scoring
• Locate and recover all missing blade pieces before installing the new impeller
• Lubricate the replacement impeller with glycerin or dish soap — do not use petroleum-based lubricants
• Align the 12-spline hub with the pump shaft and press the impeller fully into the bore
• Install the correct gasket or O-ring for the specific pump
• Tighten cover fasteners evenly
• Open the seacock and verify strong water flow at the exhaust immediately after startup

Cross-Reference Part Numbers

• Sierra: 18-3081
• Catalog ref: 47-3081
• Volvo Penta: 875811-2
• Volvo Penta: 3858256
• Volvo Penta: 3862281
• Volvo Penta: 21951346
• Volvo Penta (current ref): 24715100
• OMC: 3858256
• Johnson Pump: 09-1027B
• Johnson Pump: 09-1027B-9
• Jabsco: 1210-0001
• Jabsco: 1210-0003
• GLM: 89540
• Mallory: 9-45703
• UPC: 030999315335

Related Products

• Jabsco 1210-0001-P Neoprene Impeller Kit — Jabsco OEM equivalent for this impeller family
• Jabsco 1210-0003-P Nitrile Impeller Kit — nitrile compound alternative for the same pump family
• Johnson Pump F5B Impeller Kit 09-1027B-1 — Johnson Pump OEM service kit for F5B / 09-1027B applications
• Johnson Pump 09-1027B-10 Impeller | Volvo Penta F5B-9 — F5B-9 variant
• ARCO IP002 Volvo Penta Raw Water Pump Impeller | Replaces 21951346 / 3862281 — ARCO aftermarket alternative for the same Volvo Penta cross-reference family

Parts Desk Insights

Best use case: Sierra 18-3081 is the standard annual-service impeller for Volvo Penta raw-water pump applications in the 3858256 / 3862281 / 21951346 / 24715100 supersession chain, and for any Johnson Pump F5B or Jabsco 1210-series pump. It’s one of the most widely stocked impellers in the Volvo Penta aftermarket, making it a reliable choice when OEM lead times are an issue.

Common issues: The most frequent ordering mistake is selecting by diameter alone. The 12-spline hub and 1.243 in. / 31.6 mm width are the critical differentiators — there are visually similar impellers with the same blade count but different widths or hub styles that will not fit this pump family. Always confirm against one of the OEM cross-reference numbers above. If blade pieces are missing after removal, don’t assume they came out with the impeller — trace every downstream passage including thermostat housing, oil cooler, and heat exchanger before installing the new impeller.