Arco WP004 Mercruiser Replacement Water Pump
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Product Description
The ARCO WP004 is a complete premium replacement seawater pump for MerCruiser V8 engines equipped with a V-belt and the two-piece raw-water pump arrangement. It restores the circulation of incoming lake or seawater through the engine-cooling system and is supplied as a complete replacement pump rather than an impeller-only service kit. ARCO identifies WP004 as a direct replacement for several legacy MerCruiser and Quicksilver pump assemblies.
Key Features
- ARCO part number: WP004
- Complete replacement raw-water pump assembly
- Designed for MerCruiser V8 engines
- Fits V-belt-driven, two-piece pump configurations
- Premium replacement built to meet or exceed original-equipment standards
- Factory-tested before packaging
- Replaces multiple MerCruiser, Quicksilver and Sierra pump numbers
- ARCO Assurance Warranty coverage applies under the manufacturer's published terms.
Engine Compatibility
The strongest confirmed application is:
- MerCruiser V8 marine engines
- V-belt accessory-drive systems
- Engines using the older two-piece seawater pump assembly
Because MerCruiser V8 cooling arrangements vary by engine generation, accessory-drive layout and serial number, compatibility should be confirmed by matching the existing pump to one of the listed replacement numbers.
Serial Number Fitment Notice
Before ordering, verify that the engine uses a V-belt and two-piece raw-water pump. This pump should not be selected solely by engine displacement, as later serpentine-belt systems and one-piece pump configurations use different assemblies.
Match the original pump casting, MerCruiser part number or engine serial-number parts diagram to one of the supported references below.
When This Part Needs Replacement
Replace the complete pump when:
- Raw-water flow remains weak after installing a new impeller
- The housing is internally scored, corroded or worn
- The shaft develops excessive play
- The pump leaks from the shaft seal
- The pulley or bearing becomes noisy
- The pump repeatedly loses prime
- Engine temperature rises despite a clear intake and serviceable impeller
- The existing pump assembly is damaged or seized
Persistent cooling problems after impeller replacement can indicate wear in the pump housing, shaft, bearing or sealing surfaces rather than the impeller alone.
Installation Notes
- Confirm the engine serial number and original pump reference before removal.
- Close the raw-water intake seacock or otherwise isolate the water supply.
- Disconnect the battery before working near the belt drive.
- Note the original V-belt routing and pulley alignment.
- Inspect the belt and cooling hoses while the pump is removed.
- Replace deteriorated hoses, clamps or belts during installation.
- Align the pulley carefully with the remaining engine accessories.
- Set belt tension according to the MerCruiser service procedure.
- Prime the pump and restore the raw-water supply before starting the engine.
- Check immediately for leaks, correct belt tracking and strong exhaust-water discharge.
Professional installation is recommended where pulley alignment, belt tension or hose routing is uncertain.
Alternate / Replacement Part Numbers
The ARCO WP004 replaces:
- MerCruiser: 46-72774A32
- MerCruiser: 72774A11
- MerCruiser: 73823A7
- MerCruiser: 59112A2
- Quicksilver: 72774A32
- Sierra: 18-3600
Compatible & Related Parts
When servicing the raw-water cooling system, consider these related parts:
- Mercury MerCruiser Water Pump Repair Kit 89984T5 – impeller and seal service kit
- Mercury MerCruiser Water Pump Wear Plate 8M0180871 – wear plate replacement
- Sierra Marine Water Pump Impeller Kit 18-3077 – MerCruiser / OMC raw-water pump service kit
- Mercury MerCruiser Quicksilver Water Pump Impeller 43026T2 – OEM impeller
- Sierra 3160-1 MerCruiser Sea Water Pump – Brass – alternative pump assembly
Parts Desk Insight
The critical fitment detail is not simply “MerCruiser V8.” The WP004 is specifically for the older V-belt, two-piece seawater pump setup. Confirm the number on the existing pump or use the engine serial-number diagram before ordering, especially when working on repowered boats or engines with modified accessory drives.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.