The Impellers and Shaft Seals are normal wear items and do not have a "typical" life span. As such, it is common to change them on a regular basis; such as, with every other oil change. The condition of the raw water, i.e.: silt content, contamination, etc., contributes to the deterioration of these components and the frequency at which they should be replaced. The Impellers for both pumps are identical, but the Shaft Seals are different.
 
An exhaust temperature light going out (alarm) can indicate insufficient flow and therefore a worn raw water Impeller. The appearance of insufficient flow at the exhaust outlet can also suggest a worn raw water Impeller.
 
A falling coolant level, with no apparent leaks, can indicate a leaking raw water pump Seal (21/10). The engine coolant can follow the raw water pump shaft (21/2) through a worn Seal into the raw water pump chamber. Once in the raw water pump, the coolant will be pumped overboard with the waste raw water.

Impeller Removal
If it is necessary to replace the Seals or Impeller (21/4) in the raw water pump, follow these steps:

1. Clamp the raw water Outlet Hose (16/13) with vise grip pliers. This will prevent raw water from draining into the drip pan.
2. Remove the four screws (21/14) from the End Cap using a 7mm socket and 1/49 drive ratchet. A box or open end wrench can also be used, but not as conveniently. Pull the End Cap (21/5) off the pump. Remove the paper Gasket (21/6).
3. Grip the Impeller with long nose pliers and pull the Impeller and Shaft assembly (21/2 & 4) out of the pump body. Remove the screw (21/13) from the Impeller and slide it off the Shaft.
4. Clean the deposits off the Shaft with 400 grit paper.

Impeller Installation

1. Remove the screw from the new Impeller. Lubricate the Shaft with light grease, put the new Impeller on the Shaft and insert the screw.
2. Lubricate the Impeller, vanes, front, back, and Shaft, with light grease. Insert the Shaft into the pump body and fold the vanes as necessary to insert the Impeller into the pump.
3. Lubricate both sides of a new Gasket and place it onto the body. Align the End Cap with the body and press it onto the Shaft. Install the screws and tighten them evenly. DO NOT OVER TIGHTEN THE SCREWS!