Water Pump Impeller Kit – Fits Mercury Mariner 2-Stroke 3.5–9.8 HP (Replaces 47-89980T1, 47-89980Q1)

Product Details

This Water Pump Impeller Kit – Fits Mercury Mariner 2-Stroke 3.5–9.8 HP (Replaces 47-89980T1, 47-89980Q1) is designed for a range of Mercury and Mariner 2-stroke outboard motors, including 3.5 HP, 3.6 HP, 3.9 HP, 4 HP, 4.5 HP, 7.5 HP, and 9.8 HP models manufactured between 1979 and 1986. Please verify your specific model and serial number before ordering.

It serves as a direct replacement for multiple part numbers, including Mercury 47-89980T1, 47-89980Q1, 89980, 89980B, and 68988, as well as aftermarket equivalents like Sierra 18-3054 and GLM 12270.

• Installs in the lower unit to restore water circulation for engine cooling.
• Features a durable neoprene impeller and a stainless steel (SS316) wear plate for longevity.
• Crucial Fitment Note: This kit is for models with a .438" (11.1 mm) impeller inside diameter. Measure your existing part to ensure compatibility.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury, Mariner, and Force engines, it is critical to also check the serial number ranges listed further down to ensure this part is correct for your motor, especially regarding the .438" impeller I.D.

Serial Number Compatibility

Technical Specs

Product Type

Water Pump Impeller Kit

Installation

Lower Unit/Driveshaft

Materials

Neoprene Impeller, SS316 Wear Plate, Nylon PA66 Tube

Impeller Blades

6

Impeller Height

14.4 mm (0.57 in)

Impeller Inside Diameter

11.1 mm (0.438 in)

Impeller Outside Diameter

31.8 mm (1.250 in)

Fitting Type

Internal Shaft Mounting

Weight

23 g (0.811 oz)

What’s in the Box

• 1 x Impeller (Replaces 47-89980/89980B)
• 1 x Wear Plate (Replaces 46895)
• 1 x Woodruff Key
• 1 x Water Guide Tube Sleeve
• 3 x O-rings

Installation Notes

1. Critical Fitment Check: Before disassembly, confirm this kit is correct. Mercury used two different driveshaft diameters for these HP ranges. This kit is for the smaller .438-inch impeller inner diameter. Do not proceed if your old impeller has a larger opening.
2. Disconnect the spark plug leads to prevent accidental starting. Shift the outboard into neutral.
3. Remove the bolts securing the lower unit (gearcase) to the upper leg. Carefully lower the unit, watching for the shift shaft linkage.
4. Place the lower unit on a workbench. Unbolt and remove the water pump housing.
5. Remove the old impeller, wear plate, gaskets, and seals. Note their orientation.
6. Clean all mating surfaces thoroughly, removing any old gasket material or corrosion.
7. Install the new wear plate, gaskets, and o-rings included in the kit.
8. Slide the new impeller onto the driveshaft, ensuring the Woodruff key is in place. You may use a small amount of dish soap to lubricate the housing interior.
9. Rotate the driveshaft clockwise while pushing the pump housing down over the impeller to correctly set the blades.
10. Secure the housing with its bolts, tightening to the manufacturer's recommended torque.
11. Reinstall the lower unit, ensuring the water tube, driveshaft splines, and shift shaft are correctly aligned.
12. Once reassembled, test the engine using a water supply (flushing muffs or in a test tank) and check for a strong stream of water from the tell-tale outlet.

Troubleshooting & FAQ

Safety & Important Info

• Verify all images and specifications against your original part before purchase. Pay special attention to the .438" (11.1 mm) impeller inside diameter. If anything differs—even if your model appears compatible—do not purchase this kit.
• This is an aftermarket replacement part and is not manufactured by or affiliated with the original equipment manufacturer (OEM).
• Professional installation is highly recommended for safety, proper function, and to prevent engine damage.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested to withstand real-world saltwater and freshwater conditions.
• Fast Global Fulfillment — With warehouses worldwide, we offer free standard delivery to most regions, typically arriving in 5–15 days.
• Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials, quality control, or performance.