ARCO Marine WP001 Brass Sea Water Pump for Mercruiser V6/V8

The ARCO Marine WP001 is a complete brass sea water pump built to bolt straight onto 2000 and newer Mercruiser MCM V-6 and V-8 sterndrives. It ships as a full assembly with the impeller and mounting gasket already in the box, so you're not hunting down a separate impeller kit or gasket set before you can start the job. If your raw-water pump has started weeping at the seal, lost its prime, or your engine is creeping up the temp gauge on a hot afternoon, this is the part that gets cooling water moving through the block again.

This pump handles raw-water duty on the 305, 350, and 496 CID engines that came from the factory with the brass sea water pump, the Gen 7 style used from 2000 to the present. The sea water pump is the heart of the cooling system on a sterndrive. It pulls water in through the drive, pushes it through the engine, and sends it out the exhaust. When the impeller wears down or a vane tears off, flow drops and temps climb fast. Running a raw-water-cooled block hot is how you cook a head gasket, so a tired pump isn't something to nurse through another season.

The brass housing is the reason a lot of boaters step up to this pump. Brass shrugs off salt and brackish water far better than a composite body, and it holds its shape under heat cycling year after year. It's honest to say brass isn't bulletproof. After four or five hard seasons the mounting ears can start to pit where they meet the block, so give them a look at every impeller change. But for a boat that lives in salt or spends its summers in brackish backwaters, the brass body is the one you want.

Fitment is straightforward, with one thing to double-check. This pump is for 2000 and newer engines. If you've got a late-1990s 350 or you're not sure of the model year, verify the serial range before you order, because the pre-2000 pumps used a different pulley offset and the belt line won't sit right if you mix them. This ARCO unit cross-references the Mercury OEM part number 47-862232A2, so if you've been ordering by that number you're in the right place.

A few install notes from the folks who do this every week. The impeller vanes have to face the correct rotation, or the pump will shred them on the first startup, so mark the housing before you pull the old one apart and set the new impeller the same way. Clean the block face completely before the new gasket goes on. Old sealant residue is the number one cause of a fresh pump that still seeps. Torque the mounting bolts to 18 to 20 ft-lbs and no more. It's easy to overtighten brass and crack an ear, and then you're buying the pump twice. On the 496 CID engines, check clearance between the pump pulley and the power-steering bracket before you button it up, since they can foul each other and a thin shim usually sorts it out.

While you're in there, do the whole cooling job once. Replace the raw-water hose clamps at the same time, because the old ones tend to seize on the brass ports and you don't want to fight them next season. And if the engine has been running warm, pair the new pump with a fresh thermostat and housing. A worn pump and a sticky thermostat often show up together, and swapping only one leaves you chasing the same overheating a month later.

ARCO Marine has been building marine engine parts for nearly 60 years, and they test every unit past normal operating conditions before it ships. That's the kind of part you want feeding cool water to your engine when you're three miles out on a July afternoon. Order it, set aside an afternoon, and get your cooling system back to full flow.