thru hull removal

I’ve got to replace two Spartan Marine sea cocks (plan to order new from Spartan Marine) and am removing the thru hulls to do so. The 1" thru hull (water input to head) came out easily using what looks like a Buck Algonquin “step wrench” that I borrowed from the boat yard shop. But the same step wrench does not fit the 1 1/2" thru hull for the sink drain! It looks like the step wrench cylinder is a fraction of an inch too large in diameter and the groove (that should fit the tabs on the inside of the thru hull) is a fraction of an inch too narrow. Has anyone come across this problem? If you know of a step wrench that should work, please tell me. I’m also considering grinding off the thru hull down to the fiberglass hull and then pound it in from the outside, or getting an “internal wrench” grips the inside of the cylinder in the thru hull by expanding. Has anyone tried either of these methods? Thanks for your help.

A step wrench (aka through-hull installation tool) is a relatively expensive tool with limited use, i.e. installing and removing thru-hull fittings.

Your experience suggests that individual manufacturers might make them specific to their own through-hull fittings. The only ones I’ve ever seen for sale are from Groco (see: GROCO Thru-Hull Step Wrench | West Marine ).

Destructive removal is tempting, either with an angle grinder to remove the exterior flange in one operation, or with a hacksaw or cutting disc on the angle grinder to first make radial cuts in the exterior flange and then second to use a cold chisel to remove the slices in the pie of the flange.

The sink drain should be quite accessible, no? You can put a wrench on the hexagon of the thru-hull nut? Either the nut will back off or the thru-hull with turn. If the thru-hull turns, then all you need do is to stop it turning. A plumber’s Stilson wrench should do it. Or could you not jam something into the thru-hull from outside and have a helper hold that?

I take it that you’ve assured yourself that your existing thru-hull does need be replaced or that your new seacock will not fit on the existing thru-hull.

Thanks. The Spartan Marine seacocks bolt on with bolts that have been fastened from the outside of the hull, so cannot be turned from the inside. Removing these bolts is something I would like to avoid. The existing thru hull could be reused if I don’t have to cut it off.