SKU: CW75351
UPC: 742985175181
MPN: THXL-1500-WS
The GROCO 1-1/2" Stainless Steel Extra Long Thru-Hull Fitting w/Nut (MPN THXL-1500-WS) is a marine-grade through-hull penetration solution designed for serious boaters and anglers who demand reliability below the waterline. Whether you're upgrading a raw water cooling system, installing a livewell intake, or running through-hull plumbing for a washdown system, this extra-long fitting bridges applications where standard thru-hulls fall short. Built for vessels where hull thickness or complex backing plate configurations require extended thread length, it eliminates the frustration of bottomed-out fasteners and weak sealing surfaces.
Machined from #316 stainless steel, this fitting resists corrosion in saltwater and freshwater environments far better than standard 304 or mild steel alternatives—critical when your through-hull is in constant contact with moisture, salt spray, and temperature cycling. The extra-long NPSM/NPT combination thread design allows compatibility with both national pipe straight mechanical (NPSM) and national pipe tapered (NPT) applications, providing flexibility across different system configurations and existing plumbing standards. The included nut simplifies installation and ensures a secure backing plate connection without requiring specialized tools or additional hardware sourcing. At 1-1/2" diameter, this fitting handles substantial flow rates for engine cooling, bilge pumping, or live bait circulation without restriction.
This fitting is essential for cruising boats, fishing vessels, and trawlers with thick hulls, reinforced transoms, or multi-layer fiberglass construction where standard fittings cannot achieve adequate thread engagement. Installation requires careful measurement to confirm the hull thickness and thread requirement before ordering, as the extra-long design is intentional and not adjustable. When paired with quality hose, proper bedding sealant, and backing plates, the GROCO extra-long thru-hull fitting becomes one of the most dependable underwater penetrations on your vessel, protecting against leaks and system failure during extended runs offshore or in demanding freshwater applications.
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