Forespar Sea Strainers
Forespar Sea Strainers: Marelon Engineering for Marine Raw Water Systems
When it comes to protecting your engine and onboard systems from debris, few names carry the credibility of Forespar. A California-based marine manufacturer founded in 1966, Forespar has built its reputation on engineering products that outlast and outperform traditional metal alternatives — and nowhere is that philosophy more evident than in their line of sea strainers.
The centerpiece of every Forespar sea strainer is Marelon®, the brand's proprietary glass-reinforced composite material. Marelon is not ordinary plastic — it is the only synthetic material to be approved by the Marine Underwriters Laboratories (UL) for use below the waterline, and it has passed the same stringent tests as bronze. Beyond that, Forespar's Marelon strainers exceed ISO standards and carry approval from the American Boat and Yacht Council (A.B.Y.C.), making them a trusted choice for both production boatbuilders and serious bluewater sailors.
Why Marelon Outperforms Bronze and Standard Plastics
Traditional bronze strainers corrode, suffer from electrolysis, and can become difficult to service after years in a saltwater environment. Marelon solves all of these problems at once. The material is inherently corrosion and electrolysis resistant, will not freeze or become brittle with age, and holds up reliably across temperature extremes — a critical quality for boats that sail in both cold northern waters and tropical climates.
Forespar's sea strainer lineup spans several form factors to fit the needs of different installations:
- MF Series Raw Water Strainers — Full-size inline strainers built with a clear polycarbonate lid for easy visual inspection without removal, an easily removable stainless-steel basket for routine cleaning, and an integral mounting bracket. The MF-810, for example, handles flow rates up to 40 GPM at 1-1/2" ports, making it suitable for primary engine cooling circuits on mid- to large-sized vessels.
- T-150 Compact Strainer — A smaller-footprint model designed for tight bilge and engine room installations. It features two 1-1/2" female NPSM parallel-thread ports, supports up to 150 psi at 70°F, and includes a rotatable mounting bracket so hose routing is never a compromise.
- Thru-Hull Scoop Strainers — Precision-molded in high-strength, carbon-reinforced Marelon, these high-speed strainers feature a two-piece construction for easier installation and are available in 3/4" and 1-1/4" thread sizes. Their screens can be epoxied directly to the hull, eliminating the need for additional penetrations.
Installation Considerations
Forespar engineers its strainers around practical seamanship. NPSM (National Standard Free-Fitting Straight Mechanical Pipe Thread) ports are standard across the lineup — parallel threads that seat correctly with marine-grade fittings and avoid the mismatch problems that arise when NPT tapered threads are used in plumbing applications. A seacock on the intake thru-hull is always recommended, and Forespar advises an inline valve on the outlet side as well, so the strainer basket can be isolated for cleaning without bilge spillage.
Whether you're outfitting a new build or replacing an aging bronze strainer that's showing its years, Forespar's Marelon sea strainers represent a modern, maintenance-friendly upgrade that meets the highest standards in marine plumbing. Explore the full Forespar brand catalog or browse all sea strainers to find the right fit for your vessel.