Mercury Quicksilver NEW OEM 46-73640T01 Water Pump Base Assy 50 70 HP 76-79 0810

Mercury Quicksilver Water Pump Base Assy — Part Number 46-73640T01

Brand: Mercury Quicksilver | Condition: New Old Stock (NOS)

Genuine Mercury Quicksilver part number 46-73640T01, catalogued as Base Assembly, Water Pump — the water pump base that mounts to the gearcase and carries the impeller housing on Mercury, Mariner and Force 50 HP and 70 HP outboard lower units, approximately 1976 through 1979. The T01 suffix is Mercury's current revision of this assembly and supersedes the earlier 46-73640A1. This is new old stock from long-term dealer inventory, a genuine Quicksilver component rather than an aftermarket substitute.

The water pump base is the foundation of the entire cooling system. It bolts to the top of the gearcase, seals the water passage coming up from the pickup, and provides the machined face the impeller housing clamps against. On a motor this age the base is frequently the reason a water pump rebuild does not fix the overheating: the sealing face has corroded or eroded, the water passage has pitted through, or the mounting surface is no longer flat enough for the housing gasket to seal. Fit a new impeller to a worn base and the pump still loses prime.

Mercury's cast aluminium pump bases sit permanently in raw water, which on a saltwater motor means forty-plus years of galvanic attack. This is one of the parts that genuinely wears out rather than simply needing a service item replaced — and once dealer stock of an assembly for a 1970s motor is gone, there is nothing but used parts of unknown condition.

Condition Details

New old stock. The base assembly is unused and has never been installed. As with all warehouse-stored inventory, the packaging may show shelf wear, dust, fading, price stickers, scuffs or minor crushing from stacking. The base itself is undamaged, with the sealing face clean and flat, water passages clear, and no corrosion, pitting, cracking or distortion from storage. Please review all photos, as what is pictured is what you will receive.

Specifications

• Part Number: 46-73640T01
• Part Name: Base Assy, Water Pump — Mercury's own catalogue designation
• Manufacturer: Mercury Marine / Quicksilver
• Mercury prefix: 46 = water pump and impeller group
• Suffix: T01 — current revision, superseding the A1 version
• Location: water pump base, mounted to the gearcase beneath the impeller housing
• Package quantity: 1
• Sold: each
• Genuine OEM, not aftermarket

Overall dimensions and bolt-hole pattern are not published in the catalogue data available for this number and are deliberately not stated here rather than guessed. If you need these confirmed before you buy, message us and we will measure the actual part and send you the figures and additional photographs.

Superseded & Cross Reference Part Numbers

Mercury Quicksilver 46-73640T01 interchanges with the following. Always confirm against your own application guide before ordering.

• Mercury Quicksilver current: 46-73640T01
• Mercury Quicksilver earlier revision: 46-73640A1
• Sierra Marine: 18-3423 (water pump base)

Do not confuse this with the complete pump kit. Mercury catalogues two different parts on the same 46-73640 base number:

The A2 kit contains fourteen pieces — impeller, impeller plate, housing, base, drain screw gasket, base gasket, lower water pump gasket, three O-rings, rubber washer and exhaust leg rubber seal. This listing is the base assembly only. If you need the full rebuild kit, that is 46-73640A2, and we would rather tell you now than process a return.

Features

• Genuine Mercury Quicksilver factory assembly, produced to the original specification
• Current T01 revision, superseding the earlier A1 — the latest issue Mercury produced for this application
• New, uncorroded sealing face, so the impeller housing gasket seats flat and the pump holds prime
• Clear, unpitted water passages — the failure that makes a new impeller pointless on a worn base
• Cast construction specified for permanent raw-water immersion, including saltwater service
• Fixes the overheat that persists after an impeller change, which is the most common reason a water pump rebuild fails to solve the problem
• Correct bolt pattern and mounting geometry for the 50 and 70 HP gearcase, no modification required
• Original factory part for motors that have been out of production for over forty years

Application

Fits Mercury, Mariner and Force outboard lower units, approximately 1976 through 1979:

• 50 HP — including the 500/50 designation
• 70 HP — including 3-cylinder variants

Several serial number ranges are covered within each year and horsepower combination. Mercury catalogues parts by serial number break rather than by model year, so the serial number on your engine plate is the definitive fitment marker — more reliable than horsepower or year alone.

Buyers should confirm 46-73640T01 or 46-73640A1 against the exploded water pump diagram for their specific engine and serial range before ordering. If you send us your engine serial number we will check it against the parts catalogue for you.

Why Choose Mercury Quicksilver?

Mercury Marine has built outboards since 1939 and Quicksilver is Mercury's own parts and accessories brand — the genuine factory parts channel, not an aftermarket line. Mercury maintains serial-number-indexed parts catalogues going back decades, and Quicksilver parts are built to the specification the engine was designed around. On a water pump base, that specification is the casting itself: the flatness of the sealing face, the geometry of the water passage and the alloy's resistance to galvanic corrosion in raw water. Those are not things a used part off a salvage motor can be relied on to still have.

Returns

We accept returns through eBay's standard 30-day return request process. If the part is not what you need, simply open a return request through eBay within 30 days of delivery and we will take care of it.

Thank you for looking. We are a small parts business and we take real care in identifying, describing and packing every item we list. If anything about this part is unclear, or if you want additional photos or measurements before you buy, please message us — we would much rather answer a question up front than have you receive something that is not right for your machine.

If there is any problem at all with your order, please contact us first and give us the chance to make it right before leaving feedback. We respond quickly and we will resolve it.

QBS Parts, Inc — Gardena, CA