Check the impeller regularly and have a spare. Impellers are the heart of an engines cooling system and require regular inspection and replacement under normal operating conditions. Running through silty or sandy water or running a pump dry can ruin an impeller quickly and cause the engine to overheat. It is important to monitor cooling water outflow and replace the impeller at the first signs of reduced outflow. Sierra replacement impellers are engineered to meet or exceed Mercury and Yamaha specifications to give boaters and technicians the confidence of an OEM fit and function. These neoprene impellers are compatible with many Mercury and Yamaha 20hp—30hp (including Mercury 28hp) outboards manufactured between 1977—1997. Because unexpected failures can happen, it is important to have a spare onboard to save the day. Use our Engine Parts Selector or call 1-800-BOATING with your engines serial number to confirm this is the correct impeller for your engine. Key Features Impeller is engineered to meet or exceed manufacturer specifications OEM fit restores function and makes installation predictable Having a spare can save the afternoon and saves having to make a trip to the parts store. 18-3067 Application Guide. ApplicationOEM Part NumberGLM89890Mallory9-45600Mercury Marine47-84797M, 47-81604MYamaha Outboard689-44352-02-00, 689-44352-00-00, 689-44352-01-00The Sierra Engine Parts SelectorIn addition to impellers, we offer a wide variety of other engine parts manufactured by Sierra. To see if we have the part you need, see ourEngine Parts Selector, where you can search by engine make, serial number and model or year of manufacture