ARCO WP001 MerCruiser Brass Seawater Pump | Replaces 8M0139984 / 862914A13

ARCO WP001 MerCruiser Brass Seawater Pump

Part Number: WP001 (ARCO)  |  Brand: ARCO Marine  |  UPC: 693006030098

ARCO WP001 is a complete premium replacement brass seawater pump for compatible 2000-and-newer Mercury MerCruiser V6 and V8 engines originally equipped with the brass seawater pump assembly. It replaces the engine-driven raw-water pump responsible for drawing lake or ocean water into the cooling system and circulating it through the engine's heat exchangers and exhaust.

WP001 directly replaces Mercury / Quicksilver 8M0139984, 8M0118062, and 862914A13, and Sierra 18-3160-1. ARCO factory-tests every pump before packaging.

Important: WP001 is an ARCO aftermarket replacement pump — not a Mercury or Quicksilver OEM assembly. Confirm fitment by the original pump number or engine serial diagram, not by engine displacement alone.

Specifications

• Manufacturer Part Number: WP001
• Brand: ARCO Marine
• Product Type: Complete Seawater Pump Assembly
• Construction: Brass pump body
• Configuration: Engine-mounted brass seawater pump
• System: Raw-water (seawater) engine cooling circuit
• Weight: 2,177 g / approx. 4.8 lb
• UPC: 693006030098

Compatible Applications

Fits 2000-and-newer Mercury MerCruiser MCM V6 and V8 engines equipped with the brass seawater pump. Fitment depends on the installed pump configuration and original pump reference number. Verified engine families include:

• MerCruiser V6 (4.3L) sterndrive and inboard applications with brass seawater pump
• MerCruiser 5.0L / 305 CID V8 with brass seawater pump
• MerCruiser 5.7L / 350 CID V8 with brass seawater pump
• MerCruiser 8.1L / 496 CID V8 with brass seawater pump

Engine displacement alone is not sufficient to confirm fitment. MerCruiser engines of the same displacement can use different pump configurations depending on production year, serial number range, and accessory-drive arrangement.

Fitment Notice

Before ordering, confirm the existing pump or Mercury engine parts diagram references one of the following:

• Mercury / Quicksilver 8M0139984
• Mercury / Quicksilver 8M0118062
• Mercury 862914A13
• Sierra 18-3160-1

Do not confuse WP001 with the older ARCO WP004 V-belt, two-piece MerCruiser pump, which is intended for earlier pump configurations.

When to Replace the Complete Pump Assembly

An impeller replacement alone may not restore full cooling performance when the pump housing or shaft is worn. Replace the complete pump assembly when any of the following are present:

• Cooling-water discharge is weak even after impeller replacement
• Engine temperature rises despite a serviceable impeller
• Pump housing is internally scored, corroded, or cracked
• Water leaks from the shaft seal area
• Shaft shows excessive play or movement
• Bearing is noisy, rough, or has failed
• Pump repeatedly loses prime after impeller service
• Pulley, housing, or mounting points are damaged
• Repeated impeller failures caused by internal housing wear

Installation Notes

• Confirm the engine serial number and original pump reference number before removal
• Close the seawater intake seacock or otherwise isolate the water supply before disassembly
• Disconnect the battery before working near the belt drive
• Record original belt routing and all hose locations before removal
• Inspect the drive belt, pulley, inlet/outlet hoses, and hose clamps while the pump is accessible — replace worn components at the same time
• Clean all mating surfaces and hose connection ends before assembly
• Transfer any required pulley or mounting hardware per the service manual procedure
• Align the pump and pulley carefully before tensioning the belt to specification
• If the previous pump or impeller suffered internal damage, inspect all downstream cooling passages for missing impeller fragments before startup
• Restore the seawater supply before starting the engine
• Verify strong raw-water discharge at the exhaust outlet, check for leaks, and confirm correct belt tracking immediately after startup

Cross-Reference Part Numbers

• ARCO: WP001
• Mercury / Quicksilver: 8M0139984
• Mercury / Quicksilver: 8M0118062
• Mercury: 862914A13
• Sierra: 18-3160-1
• UPC: 693006030098

Related Products

• Mercury MerCruiser Seawater Pump Impeller Kit 8M0137219 — OEM impeller kit for brass pump service
• Mercury MerCruiser Quicksilver Impeller Kit 8M0104229 — OEM impeller kit
• ARCO IP001 MerCruiser Seawater Pump Impeller | Replaces 47-8M0104229 — ARCO aftermarket impeller for this pump family
• Mercury MerCruiser Seawater Pump Gasket 27-34897 — pump cover gasket
• Sierra 3160-1 MerCruiser Sea Water Pump — Brass — Sierra aftermarket brass pump alternative
• ARCO WP004 MerCruiser Replacement Water Pump — older V-belt two-piece pump variant for earlier configurations

Parts Desk Insights

Best use case: WP001 is the right choice when a full seawater pump replacement is needed on a 2000-and-newer brass-pump MerCruiser V6 or V8 — particularly when impeller replacement alone hasn't resolved the cooling problem, or when the housing is scored, the shaft seal is weeping, or the bearing is noisy. It's a factory-tested complete assembly that eliminates the uncertainty of reusing a worn housing with a new impeller.

Common issues: The most frequent ordering mistake is selecting WP001 based on engine size without confirming the pump model. MerCruiser V6 and V8 engines of the same displacement can use significantly different pump arrangements depending on year and serial range — always confirm against the three Mercury cross-reference numbers above. The second common issue is installing a new pump into a cooling system that still has impeller fragment debris from the previous pump failure. Even a small piece of impeller material lodged in a heat exchanger or thermostat housing can trigger overheating within minutes of startup. Inspect the full circuit before closing up.