Head Bolts, how they work

This weekend I installed a new head and had the chance to learn what Bobby told us about these head bolts and how they simply thread into the base. Well....one of my bolt/nut combos was seized up and I ended up backing the entire bolt out of the base to explore. Sure enough the bolt is simply screwed into the head floor. The interesting aspect is that the bolt is a lag screw on the bottom and a machine screw on the top for cap nut. The base seems to be built up on the underside so that these long lag screws can be threaded into the base. With this seized bolt, I simply backed it out, then mounted the head, and screwed it back in. So if your head bolts break off, I guess you could drill new holes and screw down new ones. Has anyone every broken any of these? Has anyone replaced these with new ones? These look like custom screws/bolts. Any idea where they came from?
Hayden

Here is a photo...

Thank you Bobby, Good info, good stuff. Now I know where to get new ones if I break any. Mine did look a little rusty, but I replaced them as only one backed all the way out and the others worked fine.
Hayden

MAIK:
Drilling near the head floor outside gets you very close to the hull. When I drilled into the head cabinet base, I hit the hull and that was not near the back outside wall.

I am guessing that you drilled into the hull and that you have saltwater leaking at this point. You should check into this bu pulling the boat or diving the boat.

Hayden