21 Micron Short Fuel Water Separator Filter | Sierra 18-7844 Replacement spin-on fuel filter fits many Mercury & Mercruiser marine engines to remove contaminants & water from incoming fuel. Mercury short fuel filter Protects marine engines by filtering water, dust, and dirt in fuel supply 21 micron filtration Used on many different Mercury & Mercruiser marine engines Short style filter measures 3.875 inches in length Replaces Mercury 35-807172, 35-806771, 35-802893Q, 35-802893Q01 Replaces Marine Power 395524 Replaces Mallory 9-37800 Replaces Sierra 18-7849