The water pump impeller in an outboard motor and most sterndrives is an item that should be replaced according to the service schedule in the owner’s manual. As the impeller wears, the flow of water to the powerhead can be diminished. If the impeller fails, the engine will quickly overheat. Replacing the impeller is a part of normal service performed by a marine dealer, but if you are a do-it-yourself boat owner, it’s a task that can be accomplished in the home shop.
To make water pump maintenance easier, Quicksilver® offers a complete water pump repair kit for many Mercury®, Mariner® and Force outboards, for some popular Yamaha® outboard models, and most Mercury MerCruiser® sterndrive models. For example, this 15-piece Quicksilver Water Pump Repair Kit includes a new impeller plus a new stainless steel wear plate and all of the gaskets, O-rings and seals required to complete the installation with fresh components. The kit even has a small tool used to install the new face seal on the drive shaft, an important part that’s often over-looked by home mechanics. Each kit will include parts for a specific outboard or sterndrive model. All the parts in a Quicksilver water pump repair kit are OEM quality for a perfect fit and long service life.
Depending on the outboard or sterndrive model, your owner’s manual will recommend changing the impeller annually, at 100 hours or at 300 hours. But time is not the only factor to consider when regarding impeller life. If you regularly use the motor in silty water or if you happen to run aground on a sandy bottom, abrasive material drawn through the pump can accelerate wear and changing the impeller will be good insurance against failure. A weak flow of water from the cooling water telltale is a sign the impeller may be worn and no longer pumping efficiently. If you are reviving an old motor or an outboard that has not been used in several seasons, change the impeller before starting the motor. There’s a good chance the impeller has grown stiff and taken a “set” and will either disintegrate on start up or no longer pump efficiently.
Changing the impeller does not require special tools. Before changing your impeller, get a copy of the service manual for your motor, which will have specific step-by-step instructions. Service manuals for many Mercury engines may be ordered online or through a Mercury Authorized Dealer.
With a fresh impeller, you can count on the performance of your motor’s cooling system.
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