Boat maintenance at its core is about taking things off and putting them on. Paint job? Remove the old, brush on the new. New thru-hulls? Take out the old, put in the new.
You get the picture.
Here’s a step-by-step guide on replacing a part that goes on a boat. The details will change depending on application (sealant, screw vs bolt, material of part) but in general, these are the steps that are good to follow.
1. Remove the old. Fully remove it. Clean out any old sealant, any dirt or gunk or anything. It’s worth spending some time making sure you got it all. In extreme cases, you might want to fully drill it out, fill with epoxy or even a wood bung and epoxy, and start all over again.
2. Dry fit the new. Put it in, making sure it fits well and correctly. Check for weird problems (maybe it overlaps where you don’t want it to, or sticks out too far.)
3. Drill any holes that are needed, with the part in place. Do this carefully.
4. Dry fit the part with fasteners. Do they work in the pilot holes you drilled?
5. Remove the part, clean the hole and the part. Apply sealant.
6. Fit the part to the hull.
7. Apply sealant to the fasteners.
8. Fasten the part to the hull.
9. Clean it all up!
10. Install the plug into the assembly. We used sealant with this too, as we'd prefer to keep water out. When we need to remove it, the threaded aspect of it will mean it's easy to remove (or that's the theory anyway.)
Then you need to go for a ride.