Water Pump Base 46-812966A7 for Mercury Mariner Force 40-75 HP 3 Cyl Outboard

Product Overview

Water pump base for the Mercury, Mariner and Force three cylinder outboards, the plate the impeller runs against. It replaces Mercury 46-812966A7 and crosses to Sierra 18-3445. It fits the 45, 50, 55 and 60 HP three cylinder engines from 1991 to 1997, in both the USA and Belgian built versions.

The base is the part people leave out of a water pump job. The impeller and the housing get changed and the base goes back on with its old wear ring, and the pump is still not moving the water it should because the clearance between the impeller and the base is what makes the pump work.

A base that is worn looks fine. The scoring is at the bottom of the bore, you can feel it with a fingernail and you cannot see it in a photograph. The impeller tips wear against it, the gap opens up, and the pump starts losing flow at low rpm first.

This listing is the base on its own. The impeller, the housing, the gaskets and the key are not included, so if you are doing the whole pump, order them as well.

It does not fit the Bigfoot models. The Bigfoot is the large gearcase version of the 60 HP and it uses a different pump, so check the gearcase before you order.

Specifications & Attributes

OEM Cross Reference

The 46-812966A7 is the number this base is sold under. The listing for it also quotes 46-812966A11, 812966A11, 812966A9 and 81266A3, which are Mercury numbers from the same family. Mercury used the A9 and the A11 on other builds of this pump, and we have not been able to confirm that they interchange with the A7, so if you are matching against one of those, send it to us with the engine serial number and we will check it before you order.

Sierra 18-3445 is the aftermarket equivalent and is a direct cross reference for the A7.

Compatible Engines

Seven build groups across the 45, 50, 55 and 60 HP three cylinder engines. Mercury built these in the USA and in Belgium, and the two productions carried different serial ranges, so both are listed separately.

The serial number on these engines is on a plate on the transom bracket. Match it against the range for your model and production, and if your serial sits just outside one of the ranges send it to us before ordering, because Mercury changed the pump more than once across this period.

The listing gives the fitment as 40 to 75 HP in the title, but the seven groups that it actually lists are 45, 50, 55 and 60 HP. If your engine is a 40 HP, or a 65, 70 or 75 HP, check with us first: those sizes are not in the fitment list for this base.

Bigfoot models are excluded. The Bigfoot is the 60 HP with the large gearcase, and it takes a different base and a different impeller.

What's Included

One base. No impeller, no housing, no gaskets and no drive key are included.

Key Features

Signs The Pump Base Needs Replacing

Fitting Notes

Condition & Warranty

Before You Buy

• Water pump base for the Mercury, Mariner and Force 45, 50, 55 and 60 HP three cylinder outboards
• Replaces Mercury 46-812966A7, crosses to Sierra 18-3445
• USA and Belgian production both listed, with serial ranges
• Model years 1991 to 1997
• Does not fit Bigfoot models
• Base only, impeller and housing not included
• 75 g with packaging, box 15 cm x 18 cm x 1 cm
• 30-Day Easy Returns
• Free Worldwide Shipping