There isn't much of an "Owner's Manual", but check
here in the archives for "Hunter 27" to see if it's posted.
It will show where the plumbing and wiring went when new, and where the tanks are.
No telling what mods may have been made over the past 40 years.
You say they broke the "line through the boom to the mast".
Well, it could be the out haul line, or it could be a reefing line.
Perhaps a topping lift...
If you can describe where the line was attached from the mast to the boom,
I can answer more definitively.