ARCO WP003 Volvo Penta / Indmar Ford 351 Replacement Water Pump | Replaces 3860703 / Sierra 18-3587-1
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ARCO WP003 Volvo Penta / Indmar Ford 351 Replacement Water Pump
Part Number: WP003 (ARCO) | Brand: ARCO Marine | UPC: 693006030111
ARCO WP003 is a complete premium replacement raw-water pump for compatible Volvo Penta, Indmar Ford 351, and most GM-based marine engine applications originally equipped with Volvo Penta pump 3860703. It restores the raw-water flow needed to keep the engine cooling system operating correctly when the original pump is leaking, worn, or no longer circulating water effectively. Every ARCO pump is factory-tested before packaging.
Important: WP003 is an ARCO aftermarket replacement pump — not a genuine Volvo Penta OEM assembly. Confirm fitment by the original pump number, not by engine displacement alone. Do not confuse WP003 with the ARCO WP002, which replaces Volvo Penta pump references 841640 / 856952 / 857451 for the Indmar Ford 302 family.
Specifications
- Manufacturer Part Number: WP003
- Brand: ARCO Marine
- Product Type: Complete Raw-Water Pump Assembly
- System: Raw-water (seawater) engine cooling circuit
- Weight: 1,960 g / approx. 4.3 lb
- UPC: 693006030111
Compatible Applications
Fitment is confirmed by the original pump number — not engine displacement or brand alone. Volvo Penta and marinized Ford / GM engines of the same family can use different pump configurations depending on year, serial range, and cooling-system arrangement.
- Indmar Ford 351 marine engine applications
- Most GM-based marine engine applications using pump 3860703
- Volvo Penta installations originally equipped with pump 3860703, including documented engine models:
- 430 / 430A / 430B
- 431A / 431B
- 432A
- 434A
- 500B / 501B
- 570 / 570A
- 572A
- 740A / 740B / BB740A
Exact fitment should be verified by engine model, serial number, and existing pump reference number. Related Volvo Penta pump references 857451, 856952, and 856513 are sometimes associated with the same crankshaft-driven pump family but are not confirmed as direct drop-in replacements for WP003 without verifying the pump number.
Fitment Notice
Before ordering, confirm the original pump or engine parts diagram references one of the following:
- ARCO WP003
- Volvo Penta 3860703
- Sierra 18-3587-1
Do not confuse WP003 with the ARCO WP002 (Indmar Ford 302 / Volvo Penta 841640 / 856952 / 857451) — they are not interchangeable.
When to Replace the Pump
Replace the complete pump when any of the following are observed:
- Cooling-water discharge is weak or absent at the exhaust
- Engine temperature rises despite correct coolant level
- Water leaks from the pump shaft seal or housing
- Shaft or bearing play is present or the bearing is noisy
- Pump housing is cracked or heavily corroded
- Pump shaft binds or resists rotation
- Repeated impeller failures point to internal housing wear
Installation Notes
- Disconnect the battery and allow the engine to cool completely before beginning service
- Drain the cooling system below the pump level
- Record original belt routing and pulley position before removal
- Inspect the drive belt, pulley, mounting hardware, and hose connections — replace worn items at the same service
- Clean the mounting surface thoroughly before fitting the new pump
- Install the correct gasket or sealing components per the engine service procedure
- Tighten mounting bolts evenly to the specified torque
- Confirm pulley alignment with all belt-driven accessories before tensioning the belt
- If the previous impeller lost blade material, inspect all downstream passages — hoses, oil cooler, heat exchanger — before starting the engine
- Refill the system with the specified coolant mixture; bleed trapped air per the engine manufacturer’s procedure
- Run the engine and verify strong raw-water discharge, no leaks, and stable operating temperature
Cross-Reference Part Numbers
- ARCO: WP003
- Volvo Penta: 3860703
- Sierra: 18-3587-1
- UPC: 693006030111
Related Products
- Volvo Penta Impeller Kit 3588475 — OEM Raw Water Pump Service Kit — genuine OEM impeller service kit for related Volvo Penta raw-water pumps
- Volvo Penta D6 Raw Water Pump Impeller Kit 22994993 — related OEM impeller kit
- Volvo Penta Raw Water Pump Impeller Puller Screw 3843949 — impeller removal tool for Volvo Penta raw-water pumps
- ARCO WP002 Volvo Penta / Indmar Ford 302 Replacement Water Pump — WP003 sibling for Ford 302 / Volvo Penta 857451 applications
Parts Desk Insights
Best use case: WP003 is the correct replacement when the raw-water pump on an Indmar Ford 351, a compatible GM-based marine engine, or a Volvo Penta 430–740-series installation is worn out and the original pump cross-references 3860703 or Sierra 18-3587-1. It’s a complete factory-tested assembly — not a rebuilt unit — so you start fresh with no accumulated wear.
Common issues: The most frequent ordering mistake is confusing WP003 with the WP002. Both are ARCO Volvo Penta / Indmar pumps and they look similar, but WP002 is the Ford 302 version and WP003 is the Ford 351 / GM version — they are not interchangeable. Always confirm against Volvo Penta 3860703 before ordering. On repowered boats or engines that have had previous pump replacements, the installed pump may not match the original engine spec — check the pump tag or existing pump number directly rather than relying on the engine plate.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 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.