What You Need to Know about Raw Water Strainers

An important and often overlooked component onboard a vessel is the raw water strainer, sometimes referred to as a boat water strainer or simply a boat strainer. Whatever you call it, a raw water strainer does pretty much what it sounds like--it strains debris from the raw water before it reaches the raw water pump, protecting it from damage or even worse, an early demise.

When they do happen to have a passing thought of a boat strainer, most folks connect the dots with the engine cooling system. Any boat that is raw water cooled, that is, bringing in outside water to cool the engine, must have a strainer to keep seaweed, small fish, and other nasties away from the pump. This is true whether the water flows through a heat exchanger or the engine.

Raw Water Intake Strainers

But there's more than one way to strain a fish. Think about all the possible raw water intakes on a boat, like for a live well or deck wash pump. And lots of boats have air conditioning, auxiliary generators, or even refrigerator heat exchanger systems that must be protected. There are many excellent strainers available for all these needs from top companies like Perko, Groco, and Buck Algonquin.

Toilet Strainers

These boat strainer needs could be fairly obvious, but one that might not be is the head. There are quite a few marine toilets out there that utilize raw water, and it isn't always poor cleaning habits or lack of chemicals that make some of them constantly stink. Grass, seaweed, and God knows what else can get stuck in the inlet water passage under the rim...do yourself and your passengers a favor and get a filter.

Boat water strainers are available in different shapes and sizes, as some vessels might be limited in space and accessibility. As for the exact model and mesh size you need, that will depend upon where it will be mounted (below or above the waterline), and what type of raw water intake (an AC unit? A live well, or engine?). The same goes for material.

A good raw water strainer is often cast in stainless steel or bronze, with a stainless steel, Monel, or plastic removable strainer basket inside. All these components have good anti-corrosive properties that are essential in a marine environment, especially a saline one, although many boaters maintain that Monel or plastic baskets are the best in salt water. 

Although there are some folks out there who use the plastic raw water strainers for every intake, there's many an old salt who will insist that plastic strainers should not be used below the water line, although they're fine for everything else. This is because--at least, with the type that has the threaded knob on top--if you inadvertently crank down too hard on the cover nut, the plastic lid supports underneath the knob can break. Not something you'd want for a below-the-water-line unit.

It is also common practice to install a scoop strainer over the raw water inlet through-hull such as manufactured by Groco, Perko or Buck Algonquin that add an extra layer of protection against sucking up debris. There are also round strainers available, without hinges or with hinges, like this one from Groco.

Boat Strainer Parts

Raw water strainer parts eventually wear out, especially gaskets, O-rings, and sight glass. But we have you covered here at Go2marine with plenty of these and other replacement parts. Sometimes you may find when it's time to replace a part that the part number is no longer valid, or the part has been superseded with an alternative. No worries, we still have you covered--just give us a call at 800-998-9508, and we will get it for you.