Sierra 18-3215 Impeller Repair Kit, Replaces Mercury 47-85089T7, Fits 15-25 HP 2-Stroke Outboards

The Sierra 18-3215 Impeller Repair Kit is a water pump impeller service kit built for Mercury and Mariner outboard motors in the 15 to 25 hp range with 2 cycle (2-stroke) engines. The kit is engineered to meet or exceed the quality of the original equipment part it replaces, giving boat owners a reliable way to restore proper cooling water flow through the outboard's water pump without sourcing a factory-branded part. Components are made from a combination of stainless steel and marine-grade composites, materials chosen for their resistance to corrosion and wear in continuous saltwater and freshwater cooling system service. The impeller itself is white in color and is designed as a direct fit replacement for the applicable Mercury/Mariner water pump housings, so installation follows the same procedure as the original part. Because outboard water pump kits are fit specific, buyers should confirm the part number against their existing pump housing or engine documentation before ordering to ensure proper fit. This kit ships as a single unit count and is intended for outboard motors using a transom mount configuration and gasoline fuel. Regular impeller replacement is a routine maintenance item that protects the engine from overheating caused by reduced raw water flow, making the Sierra 18-3215 a practical stocking item for outboard owners performing scheduled water pump service.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3215
• Product Type: Impeller Repair Kit
• Engine Type: 2 Stroke
• Maximum Horsepower: 25 Horsepower
• Fits: Various 15 thru 25 hp 2 cycle outboards
• Material: Stainless Steel, Marine-Grade Composites
• Color: White
• Mounting Type: Transom Mount
• Fuel Type: Gasoline
• Operation Mode: Motor
• Unit Count: 1
• UPC: 030999315748
• Weight: 0.29 pounds

Fitment

• Mercury/Mariner outboard motors
• Various 15 thru 25 hp 2 cycle (2-stroke) outboards

Replaces (OEM)

• GLM 12107
• Mercury 47-85089T7
• Mercury 47-85089Q4

Frequently Asked Questions

What engines does the Sierra 18-3215 impeller kit fit? The Sierra 18-3215 Impeller Repair Kit fits various 15 thru 25 hp 2 cycle (2-stroke) Mercury and Mariner outboard motors. Since water pump kits are fit specific, confirm the part number against your existing housing before ordering.

What OEM parts does the 18-3215 kit replace? It is designed to be interchangeable with GLM 12107, Mercury 47-85089T7, and Mercury 47-85089Q4, so it can be used as a direct replacement for any of those part numbers.

Is this a genuine Mercury part or an aftermarket replacement? The 18-3215 is a Sierra-branded aftermarket impeller kit, not a Mercury-branded part. It is built to meet or exceed the original equipment part it replaces.

What material is the impeller made from? The Sierra 18-3215 kit uses stainless steel and marine-grade composite materials, chosen for corrosion resistance in outboard cooling water systems.

How much does the Sierra 18-3215 impeller kit weigh? The kit weighs 0.29 pounds.

What color is the impeller in this kit? The impeller included in the 18-3215 kit is white.

How many pieces come in the box? The Sierra 18-3215 is sold as a single unit count kit containing the impeller repair components for one water pump service.

Will this kit work on a 4-stroke outboard? No. The 18-3215 kit is built for 2 cycle (2-stroke) Mercury/Mariner outboards in the 15 to 25 hp range, not 4-stroke engines.

Does the Sierra 18-3215 use a transom mount configuration? Yes, this impeller kit is intended for outboards using a transom mount configuration and gasoline fuel.

Why does the water pump impeller need periodic replacement? The impeller in a water pump wears over time, and a worn impeller reduces raw water flow to the engine, which can lead to overheating. Replacing it with a kit like the Sierra 18-3215 restores proper cooling water flow.