Are your seacocks the old-fashioned (but still the best) bronze lever-and-cone type such as Blake’s? If so, when you’re servicing them this spring, it’s a safe bet that at least one will be unwilling to come loose after you’ve unbolted the flange. Rather than unhinge your insides trying to wrestle it free in the inevitably impossible position it occupies within the hull, go outside, stick a hefty old screwdriver up the hole until you feel it ‘bottom’, then give it a sharp tap with a useful hammer. As they say, ‘every one a coconut!’ Just make sure anyone in the vicinity of the heads stands well clear.