ARCO WP003 Raw Water Pump for Indmar Ford 351 and GM Engines

When an inboard starts creeping up the temp gauge on a hot afternoon, the raw water pump is the first thing most techs check. The ARCO WP003 is an OEM premium replacement raw water pump built for Indmar Ford 351 engines and most GM inboards. It's the engine-mounted pump that pulls lake or sea water through the raw water side of your cooling system and moves it through the engine to carry heat away. When the impeller wears down or the housing starts to weep, water flow drops off and temperature climbs fast. This part puts that right.

ARCO ships the WP003 as a complete impeller and housing assembly. You're not rebuilding a tired pump or chasing down a separate impeller, cover plate, and body. You get the whole unit ready to bolt on, which is the way most owners want to handle a cooling failure that already cost them a day on the water. Swap the pump, prime the system, and you're back to running cool.

Who's this for? Ski and wakeboard boat owners running Indmar Ford 351 power, and a wide range of GM-based inboards. If your boat came with one of those engines and the water pump is original, weeping, or pushing weak flow at the outlet, this is the replacement. Not sure it's your exact pump? Every raw water pump carries an OEM part number, and the WP003 cross-references the common ones. We've listed those numbers in the specs below so you can match them against the pump that's on your engine right now before you order.

A failing raw water pump doesn't always let go all at once. Sometimes it's a slow thing. You notice the engine runs a few degrees warmer than it used to, or you spot a rusty drip under the pump after a weekend out. That drip is usually the weep hole telling you the seal is going. Left alone, a worn impeller sheds vanes into the cooling system, and now you're not just replacing a pump, you're fishing rubber out of your heat exchanger or exhaust elbows. Catching it early and dropping in a fresh WP003 is the cheap way out.

ARCO has been building marine engine parts since 1960, out of Pensacola, Florida. That's not a marketing line, it's why shops keep going back to them. Every unit gets tested and retested past normal operating conditions before it ships, so what shows up in the box behaves like the part that left the factory on your engine. For a component that stands between your engine and an overheat on open water, that track record matters.

Installation is a job most hands-on owners can handle with basic tools, though access depends on your boat. On tight ski and wake hulls, the pump can sit close to the exhaust manifold, so give yourself room and let the engine cool first. Reuse or renew your mounting gaskets per your engine's service procedure, snug the fasteners evenly, and check for leaks at first start. If you'd rather have a shop do it, ARCO's warranty even reimburses professional-installation labor on a unit they determine to be defective, which is a level of backing you don't see on every replacement pump.

How often should you touch a raw water impeller? There's no single number, but plenty of owners make it part of their regular service, checking it at the start of the season and replacing it on a sensible interval based on hours and water conditions. Boats that run in sandy, silty, or debris-heavy water wear impellers faster. If you've been putting it off and you're already in there, replacing the full pump assembly with the WP003 saves you from opening it back up next season.

Bottom line, the WP003 is the straightforward, OEM-quality fix for a raw water pump that's past its prime on an Indmar Ford 351 or GM inboard. Complete assembly, made in the USA, backed by a company that's been doing marine cooling for over sixty years. Confirm the cross-reference, get it on the engine, and get back to running cool.