How Often Should A Boat Impeller Be Replaced?

Most inboard and sterndrive boats utilize a raw water system to cool the engine while it runs. Cold water cycling through the system keeps the engine at a safe operating temperature. Boats use impellers to take in raw water. An impeller is a hub with flexible rubber fins. When the impeller rotates, water is sucked into the cooling system.

Despite being made of rubber, impellers tend to be durable. During operation, water keeps them lubricated and prevents damage. That being said, the potential engine damage from a failed impeller is substantial. Without the impeller, your boat’s engine will overheat.

boat impeller graphic

As a boat owner, it’s important to pay attention to the condition of your impeller. Regular seasonal inspections and replacements can prevent major headaches and expenses down the road.

What causes boat impellers to fail?

Like any moving component, rubber impellers will wear out after years of use. There are a few factors that can speed up impeller failure.

Damaged Boat Impeller

Sandy or muddy water 

If the body of water you take your boat out on is especially muddy or sandy, the life of your impeller can be reduced. Sand particles are abrasive and can quickly wear out the rubber veins of the impeller.

Dry running your boat

Rubber impellers rely on water to keep them lubricated. If your boat runs for even a few minutes (or even seconds) without water flowing through the impeller, it will shred and need to be replaced.

Sitting to long

Rubber becomes brittle and dry rotted if it is sits for too long . If you use your boat infrequently, or if it has been sitting for a few years, the impeller may have become brittle enough to fail on initial startup.

What happens when the impeller fails?

If the impeller on your boat breaks or fails, the resulting damage can destroy your engine. Without a constant supply of cold water, the engine will quickly overheat. When an engine overheats, damage to the head gasket, cylinders, and the engine block is possible. Severe damage may require an engine replacement.

How often should a boat impeller be changed?

Even if no abnormal damage is caused to the impeller, it should still be replaced on a regular schedule. Depending on how much you use your boat, impeller replacement should be done based on either hour of operation or years.

At Matson Point S, we recommend an impeller replacement every 100 hours of operation. It can take a long time to clock 100 hours, so we also recommend that the impeller is replaced every other year for the majority of outboards and sterndrives.

The one exception to this rule would be MerCruiser systems. The design of these units extends the life of impellers. MerCruiser impellers should be replaced every three years.

Let Matson Auto and Marine replace your impeller

Impellers are an inexpensive component. Staying on top of this boat service can save you thousands of dollars down the road. Our team of boat technicians has the skills and experience needed to service your boat. If it’s time for a new impeller, give Matson Auto and Marine a call today or schedule an appointment online!

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