ARCO WP004 Sea Water Pump for MerCruiser V8, V-Belt & 2-Piece Pump
ARCO WP004 Sea Water Pump for MerCruiser V8, V-Belt & 2-Piece Pump — Product description
The ARCO WP004 is a complete sea water pump for MerCruiser V8 engines running a V-belt and the two-piece pump housing. You get the impeller and housing together, built to OEM standard or better. If your V8 is running hot or the old pump is weeping, this is the bolt-on fix that gets your cooling system healthy again.
Your raw water pump is the heart of the cooling system on an inboard or sterndrive MerCruiser V8. It pulls sea water in through the drive, pushes it through the engine and the exhaust, and keeps everything from cooking on a hot summer afternoon. When it starts to go, temps climb, and a pump that quits offshore turns a good day into a tow. The ARCO Marine WP004 is a complete OEM-quality replacement sea water pump built for MerCruiser V8 engines running a V-belt and the two-piece pump housing.
This is the full impeller-and-housing assembly, not just a rebuild kit. You get the pump body and the impeller together, ready to bolt on. That matters when the old housing is scored or the bearing is shot, because you're not trying to save a worn part that's going to give you trouble again next season. ARCO has been building marine engine parts for nearly sixty years, and they test every unit past normal operating conditions before it ships. For a part that lives its whole life pumping salt water, that kind of reliability is exactly what you want.
Fitment is the first thing to nail down. This pump is for V8 MerCruiser engines with the V-belt drive and the two-piece pump. If your engine runs a serpentine belt or a one-piece engine-mounted pump, this isn't your part. So check what you've got on the boat before you order. A quick look at the belt and the pump housing on your current setup tells you which family you're in. If you're not sure, send us your engine model and serial number and we'll help you confirm.
A few things we've learned from swapping these out. First, replace the impeller as part of the job, and never reuse a tired old impeller in a new housing. A cracked or set vane will overheat the engine within minutes of firing it back up. Second, check your pulley alignment when the belt goes back on. A misaligned pulley chews belts and puts side load on the pump bearing, which is what kills a lot of the pumps we see come through. Third, on the two-piece housing, replace the O-ring at the seam. That seam is the classic slow drip after an impeller change, and a two-dollar O-ring saves you from chasing a leak later.
Most of these pumps give up somewhere around the 300 to 400 hour mark, and sandy or silty water speeds that up. Sand ingestion scores the shaft and eats the impeller, so if you run shallow, skinny, or dirty water, inspect the pump more often than the boater who runs clean, deep water. Signs it's time: creeping temperature at cruise, weak water flow out the exhaust, or a weep of water from the pump body. Catch it early and you're doing a planned dockside job instead of a limp-home.
Who's this for? Any boater running a MerCruiser V8 sterndrive or inboard who wants an OEM-grade pump without the dealer markup. Weekend cruisers, saltwater anglers, and anyone doing their own maintenance who'd rather install a complete assembly once than fight a rebuild. It's a straightforward job with hand tools if you're comfortable working around the engine, and it's one of the highest-value pieces of preventive maintenance you can do on a raw-water-cooled V8.
Bottom line, if your MerCruiser V8 is running hot or the old pump is leaking, the ARCO WP004 gets your cooling system back to healthy with a part built to OEM standard or better. Pair it with a fresh impeller and a new O-ring, get your pulley alignment right, and you're set for a lot of hours on the water.
Key Features
- Complete impeller-and-housing sea water pump assembly, bolt-on replacement (no rebuild required)
- Engineered for MerCruiser V8 engines with V-belt drive and the two-piece pump housing
- OEM-quality-or-better construction from ARCO Marine, nearly 60 years building marine engine parts
- Every unit tested beyond normal operating conditions before it ships
- Restores full raw-water cooling flow to protect the engine from overheating
- Ships with the impeller so you install a fresh pump, not a worn rebuild
- Direct replacement for a scored, leaking, or seized factory sea water pump
- Built to run in salt water for long, dependable service life
Why Buy from NVN Marine
- Authorized ARCO Marine reseller, full manufacturer warranty
- NMEA member and ABYC certified, advice from real boat techs
- Same-day shipping before 3 PM ET on in-stock items
- NY headquarters and Fort Lauderdale flagship retail store
Technical specifications
| Title | ARCO WP004 Sea Water Pump for MerCruiser V8, V-Belt & 2-Piece Pump |
|---|---|
| Brand | ARCO Marine |
| Manufacturer Part Number | WP004 |
| UPC | 693006030173 |
| Keystone Part Number | A4RWP004 |
| Component | Sea Water Pump (Impeller & Housing) |
| Engine Application | MerCruiser V8 |
| Belt Drive | V-Belt |
| Pump Design | Two-Piece Pump Housing |
| Replacement Type | OEM Replacement |
| Includes | Impeller & Housing |
| Cooling Type | Raw Water / Sea Water Cooled |
Frequently asked questions
Will this fit my MerCruiser V8?
It's built for V8 MerCruiser engines that use a V-belt drive and the two-piece pump housing. If your engine runs a serpentine belt or a one-piece engine-mounted pump, this isn't the right part. Check the belt and pump style on your current setup, and if you're unsure, send us your engine model and serial and we'll confirm.
Does the pump come with an impeller?
Yes. This is the complete impeller-and-housing assembly, so the impeller is included. You're installing a whole fresh pump, not just a housing that needs a rebuild kit.
What's the difference between the V-belt pump and the serpentine-belt pump?
They're two different drive setups on MerCruiser V8s. This pump is for the older V-belt style with the two-piece housing. Serpentine-belt engines use a different pump, so match the part to what's actually turning your pump.
Do I really need to replace the impeller when I do the pump?
Always run a fresh impeller. Reusing an old, set, or cracked impeller in a new housing is the fastest way to overheat the engine within minutes of restart. This assembly comes with a new impeller so you're covered.
How often should a raw water pump be replaced?
Most give up around the 300 to 400 hour mark. Sandy or silty water shortens that because grit scores the shaft and chews the impeller. If you run shallow or dirty water, inspect it more often.
How do I know my sea water pump is failing?
Watch for creeping engine temperature at cruise, weak water flow coming out the exhaust, or a weep of water from the pump body. Any of those means it's time to service or replace the pump before it strands you.
Is this a genuine OEM part?
It's an ARCO Marine OEM-quality-or-better replacement. ARCO has built marine engine parts for nearly sixty years and tests every unit beyond normal operating conditions, so you get factory-grade reliability at a fair price.
Should I replace the housing O-ring too?
Yes, on the two-piece housing, always fit a new O-ring at the seam. That seam is the classic spot for a slow drip after an impeller change, and a cheap O-ring saves you from chasing a leak down the road.
What warranty comes with it?
Full ARCO Marine manufacturer warranty applies. We're an authorized ARCO reseller, so any warranty claim runs through us straight back to the manufacturer.
