Mercury Marine water pump impeller washer – 12-8M0027721 is a genuine OEM washer for the water pump impeller in the gear housing of compatible Mercury and Mariner outboard engines. The washer is installed at the impeller on the driveshaft as part of the water pump assembly.
The spare part is documented for a range of engine families from F9.9/F15 323cc as well as selected 13.5, 15, 20, 25, 30, 40, 45, and 50 HP models. Compatibility depends on the engine's serial number and gear housing variant, so the part number must be checked in the relevant spare parts catalog before ordering.
On relevant spare parts diagrams, the washer is used in two positions around the impeller. However, this OEM spare part is sold individually, so the required quantity must be determined based on the specific water pump assembly.
Mercury Marine 12-8M0027721 replaced previous part numbers 12-86645 and 12-866451. The part has subsequently been superseded by part number 12-8M0204722.
Key featuresGenuine Mercury Marine OEM spare part
Part type: Impeller washer
Application: Water pump in gear housing
For compatible Mercury and Mariner outboard engines
Sold individually
Previous numbers: 12-86645 and 12-866451
Superseded by: 12-8M0204722
Check serial number and gear housing variant before purchase
