Mercury/Mariner Marine Outboard Water Pump Impeller

Impellers pump cold water into your boat's engine to cool it down while in use. If you have a bad impeller it can cause big problems. Impellers are critical to engine cooling systems, take along a spare.

Mercury outboard engines rely on the water pump for cooling. The impeller is the heart of the water pump; inspection and replacement is required on a regular basis to keep the engine running at optimum temperature. Mercury recommends changing the impeller every 300 hours... it's in the owners manual. It's an easy enough job to do yourself if you have some mechanical skills. Mercury and Mariner are the same company, both owned by the Brunswick Corp. Mariner was originally an Australian-licenced company that re-badged overseas engines and sold them locally under the 'Mariner' brand name, mostly US-made Mercurys and a few Johnsons. Signs of a bad boat impeller are either boat engine overheats when you try to accelerate, loss in impeller vanes flexibility, physical wear & tear like cracks in impeller vane roots, melted or worn-off vanes. Even if you see less or no water coming out of the tell-tale, it might be due to a bad impeller. Impeller pumps generally fail in one of two ways. This is usually caused by running the impeller pump dry. Remember, the fluid being pumped provides the cooling and lubrication for the pump. This is often caused by a water inlet seacock not being opened or a plastic bag covering the water inlet. Your boat's impeller is a series of rubber vanes molded around a hub. The tips of these flexible vanes can wear out for many reasons due to simple use or if the boat is in sandy water. Impellers can also wear out by becoming stiff and brittle due to the motor sitting unused for several seasons or being exposed to heat. These flexible vane tips wear out for several reasons, none of which can be prevented. Most marine engines will have a raw water pump with a flexible impeller. It is used to pump raw water from outside the boat through the engine's raw water cooling plumbing. These impellers are very reliable, but some care is required. They should never be run dry.

Mercury/Mariner Marine Outboard Water Pump Impellers are critical to engine cooling systems, so take along a spare. Mercury outboard engines rely on the water pump for cooling. The impeller is the heart of the water pump; inspection and replacement are required on a regular basis to keep the engine running at optimum temperature.