Yamaha Water Pump Replacement Protocol

Department: Cooling Systems | Level: Intermediate | Est Cost: $75

The water pump impeller is the most critical service item on an outboard motor. Yamaha specifies a 100 hour or 1 year replacement interval. Failure to adhere to this schedule leads to impeller fragmentation, which clogs cooling passages and causes catastrophic powerhead overheating. This guide details the removal of the specific Yamaha Driveshaft Collar and the correct installation of the new impeller.

Section 1: Required Tooling and Parts

Yamaha utilizes a unique retention system for the water pump housing involving a locking collar. Removal requires a specialized puller insert.

Essential Service Tools

• Driveshaft Collar Puller Adapter (AMT0013): Included with the Upper Bearing Carrier Pullerr (AMT0016) This split ring adapter engages the collar without slipping.
• Woodruff Key Removal Tool: Required if the key is seized to the shaft (which happens frequently in saltwater environments).
• 14mm and 12mm Sockets: For lower unit removal and pump housing disassembly.
• Drill and High Quality Bits: For drilling out seized woodruff keys.

Consumables

• Water Pump Kit: OEM Yamaha kit (ensure it matches your specific horsepower).
• Marine Grease: For coating the impeller cup and bolts.
• Anti Seize: Recommended for the lower unit mounting bolts.

Section 2: Lower Unit Removal

1. Hidden Bolt Removal

Remove the trim tab zinc anode located above the propeller. On many Yamaha models, there is a hidden 14mm mounting bolt located directly under this anode. Failure to remove this bolt will result in a cracked gearcase housing if you attempt to pry it off.

2. Speedometer Pickup Caution

As you lower the gearcase, watch for the small black plastic speedometer tube on the leading edge. It connects to the midsection. Do not yank the gearcase down; gently disconnect this tube. If it snaps, you lose speedometer function.

Section 3: Disassembly and The Collar Problem

3. Removing the Housing

Remove the four 12mm bolts securing the plastic water pump housing. Lift the housing off the driveshaft. You are now exposed to the Yamaha Driveshaft Collar, a stainless ring that holds the impeller assembly down.

4. Pulling the Collar

The collar is often salt welded to the shaft.
The Solution: Slide the Collar Adapter Insert between the stainless collar and the nylon spacer below it. Attach the puller jaws to the adapter. Tighten the lifting screw. The collar will pop loose instantly.

5. The Seized Woodruff Key

If the key is seized, do not beat it with a hammer. You will bend the driveshaft.
Technique: Drill a small pilot hole into the center of the key. Use a punch or an air hammer with a chisel bit to carefully rotate the key out of its slot. Heat should be a last resort to avoid melting nearby oil seals.

Section 4: Reassembly Protocol

6. Wear Plate and Gaskets

Clean the aluminum base. Install the new gasket and wear plate. Apply a light film of grease to the wear plate surface to prevent dry running during the first startup.

7. Impeller Installation

Slide the new impeller down the shaft. Align the keyway groove with the woodruff key. Press down until fully seated.

8. Housing Installation (The Spin)

Apply grease to the inside of the stainless steel cup insert. Slide the housing down over the impeller.
Critical Step: While pushing the housing down, rotate the driveshaft CLOCKWISE. This presets the impeller vanes in the correct direction. If you force them down backwards, they will flip upon startup and potentially crack.

9. Reinstalling the Collar

Place the wave washers and nylon spacer back on top of the housing. Slide the stainless collar down. Use the puller adapter (in reverse) or a deep socket to tap the collar down until it locks the spacer in place. You must pull UP on the driveshaft while tapping the collar DOWN to remove play.

Conclusion

Water pump failure is preventable. By using the correct collar puller and following the clockwise rotation rule, you ensure your cooling system operates at factory efficiency.

For more cooling system tools, visit the Marine Tech Lower Unit Section.