CHANGE YOUR IMPELLER

Outboard Motor Impeller: When and How to Maintain It

The Role of the Impeller in an Outboard Motor

The impeller, sometimes referred to as a pump wheel or "impeller" in English, plays a vital role in your outboard motor's cooling system. Its primary function is to circulate water to maintain an optimal temperature in the engine while it is running. Here are its main functions:

Cool the Engine: The impeller draws water from outside the boat and circulates it through the engine, expelling the heat generated during operation.

Prevent Overheating: Without a functional impeller, the engine can quickly overheat, damaging internal components and reducing its lifespan.

Ensure Optimal Performance: A well-maintained impeller ensures that the engine operates at a stable temperature and helps avoid overheating-related failures.

Two Essential Tips:

Always check the pee hole (or water outlet). If water is no longer flowing, immediately stop the engine. This indicates a malfunction in the cooling system.

Never run the engine without water. Running the engine without the impeller drawing water can immediately damage the impeller and lead to rapid engine overheating, which can cause severe engine damage.

Signs That the Impeller Needs to Be Replaced

The impeller is a wear-and-tear part, and like any mechanical component, it will eventually show signs of weakness. Here are the main signs to look for to know if your impeller needs replacement:

Decreased Water Flow:

If you notice that not much water is coming out of the pee hole or the water pressure is low, this could be a sign that the impeller is in poor condition.

Engine Overheating:

If your engine overheats after only a short time of use, it’s likely that the impeller is no longer circulating water to cool the engine.

Visible Wear on the Impeller:

Typically, the impeller should be replaced every 1 to 2 years or after heavy use. Visually, if you notice that the vanes are no longer straight, cracked, or damaged, it’s time to replace the impeller.

How to Replace the Impeller on an Outboard Motor

Secure the Engine

Turn off the engine and disconnect the battery.

Remove the Lower Unit

Remove the shift rod (depending on the model) and the bolts, including sometimes the one hidden under the anode.

Remove the Old Impeller

Use a flathead screwdriver or spatula to carefully lift the old impeller. Be cautious not to lose the key (clavette).

Install the New Impeller

Remove the stainless steel plate to inspect the condition of the lower unit around the water intake. Clean the plate thoroughly, as salt or limescale buildup can prematurely damage the new impeller. Also, check and clean the stainless steel housing in the pump body.

Grease the key, the pump body bolts, and the bolts used to secure the lower unit, as well as the stainless steel housing.

Check all seals and replace them if necessary, using a complete impeller kit.

Reassemble the Lower Unit

Grease the shift rod connection to ensure it can be easily disassembled during the next maintenance.

Reattach the lower unit and tighten the screws, making sure they are properly greased.

Test the Engine

Check the water flow and ensure that the engine does not overheat.

Additional Tips

Check the impeller regularly.

Never run the engine without water.