Groco Flush Mount Bronze Thru-Hull Fittings are threaded with NPS (straight) male pipe threads and are designed for use with Groco Seacocks or any similar product with NPS female threads.
These thru-hull fittings can also be used with NPT (tapered) threads in low pressure installations only. When connecting to tapered threads, a generous amount of pipe sealant or PTFE thread tape is absolutely required.
Groco thru-hulls are the best choice for below the waterline installations. Available with or without the bronze locknut with a bonding screw, or may be threaded directly into a compatible seacock.
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How do you cut the tapered hole for a flush thru-hull?Thanks.Peter.
Peter,My C&C 36 originally had tapered thru-hulls that had a wider tapered flange than this Groco that I'm using here. I had to use thickened Epoxy faring compound to fill the space left by this smaller flange.If I was setting these in flush to the bottom, not re-fitting, then I would grind the opening just deeper than the tapered flange, apply neat epoxy to the newly exposed laminate then finish the installation with thickened epoxy fairing compound for the final fit. If you heavily wax the fitting, you can carefully screw it in and press it's impression into the curing fairing compound which greatly reduces sanding/grinding. It takes a bit of effort, but you get a fair smooth bottom and unbroken water flow across it. Bill