Seacocks should thread on to the thru hull
fittings, not glue on the thru hulls.They may glue on, just never seen it done that way, SCARY to me if done that way IMOH..
I replaced all the thru hulls on our boat by lightly tapping the plugs in like you are talking about doing. The only one that was a problem was the engine
intake because it has a screen
over it. Just used a piece of plastic sandwich bag over it and open the valve. Suction holds it in place with just a little leakage...
Not exactly recommended, but I was at the yard and could get pulled if necessary,,