Mercury Mariner Water Pump Housing Insert 70977

Mercury 70977 is a genuine OEM water pump housing insert used in older Mercury and Mariner outboard lower-unit water pump assemblies. Current Mercury dealer references show 70977 superseded to 70977T, and current model-specific parts diagrams identify the active part as INSERT, WATER PUMP HOUSING in the gear housing / driveshaft service area.

Key Features

• Genuine Mercury Marine OEM part number 70977, superseded to 70977T.
• Current application references identify it as INSERT, WATER PUMP HOUSING.
• Used in the lower-unit gear housing / driveshaft water pump assembly.
• Current dealer shipping specs for 70977 are approximately 0.02 lb, 1.25 in. x 1.25 in. x 0.75 in.
• Current dealer shipping specs for 70977T are approximately 0.03 lb, 1.13 in. x 1.13 in. x 0.83 in.

Engine Compatibility

The strongest supportable fitment for 70977 / 70977T is older Mercury and Mariner outboard gear housing water pump service. Current Mercury dealer where-used references connect it to a broad range of smaller and mid-range outboards including 3.5 HP, 3.6 HP, 4 HP, 4.5 HP, 7.5 HP, 9.8 HP, 40 HP, 45 HP, 75 HP, and 110 HP model families across listed serial ranges.

Serial Number Fitment Notice

Verify fitment by exact outboard serial number and the correct gear housing / water pump parts diagram before ordering. This insert appears across many older Mercury and Mariner lower units, so serial-based confirmation is the safest way to match the correct pump service part.

When This Part Needs Replacement

Replace this insert when the water pump housing service area shows wear, distortion, heat damage, or deterioration during an impeller rebuild. Because it is part of the water pump housing stack, replacing a worn insert during pump service is often the better repair than reusing a damaged component. This is a practical service inference supported by its documented role in the water pump housing assembly.

Installation Notes

Install this part only after confirming the correct Mercury or Mariner lower-unit diagram for the outboard being serviced. Current parts diagrams show the insert used with related water pump parts such as the impeller, face plate, water pump cover assembly, water pump cover seal, and impeller drive key / pin, so it should be matched to the correct pump stack during reassembly.

Alternate/Superseded Part Numbers

Current references show 70977T as the active replacement for 70977. Related cross-reference sources also associate 46894 and Sierra 18-3113 with this insert-cup / water pump insert application.

Parts Desk Insight

With water pump parts like this, the important match is the exact lower-unit pump layout. Small pump inserts can look interchangeable, but checking the serial-number-based gear housing diagram first is the best way to avoid getting the wrong water pump housing piece.

Shipping: Ships same or next day for fast Canada wide shipping.