Join Date: Aug 2006
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Re: Thru Hull Removal Advice Request
I have a 1979 Sabre MKI and the original flush mount thru-hulls were glassed over on the outside of the hull. The interior/bilge side has a wood block glassed over. To access the outside I used a 4.5 inch flap disc on my grinder to take down about 3/8 ths to 1/2 inch of glass directly over the thru hull. Be careful with the flap disc it takes a lot of material quickly. I then used a Festool 150 sander with 80 and 120 grit rubin sandpaper and vacuum to fair the area to about 12:1 from the center of the thru-hull. The hull/hole was shaped to fit a flush mount thru-hull which provided a good seat for the back of the thru-hull head into the hull.
I have replaced with the Sparten bronze thru-hull which more or less matched the original thru hull(s). Then glassed and epoxied the area, barrier painted then bottom painted. Essentially I used Maine Sails methods as you plan. I did thru bolt where I had access and some I reused the original method of two 1.25 inch stainless lag screws into the glassed block. I filled the original holes of the lag screws with thickened epoxy. did the same for the new holes and set the screws in the thickened epoxy.
I would be hesitant to ream out the hole but rather slowly and carefully remove the glass around the thru hull (i.e., on the outside and inside). I would start on the outside. You also might find once you remove the outside glass the thruhull might just spin free with a step wrench, again using Maine Sails methods.
I had trouble with one thru hull spinning so I used a narrow demolition blade on a saz-all and made four cuts (i.e., north, south, east and west) from inside the 1.5 inch diameter thru hull (that is stick the blade in the thru hull hole) and stopped immediately as I cut through through the metal or nearly so , since I (or you will) wanted to preserve the integrity of the thru hull hole. A pry bar and hammer used gently, with a wood shim against the hull to protect from damage, got the beast out of the hole.