A torque test tells you very little other than they were slightly loose or tight. It will not tell you if they were leaking or if there is oxygen deprived salt water trapped in there eating away at the stainless. It may also do nothing for you if the keel stub is already leaking other than to allow it to continue leaking despite tight keel bolts. If the bolts are loose, or even tight, and the joint is leaking, you will often see signs.
If it looks like this the keel should be dropped, bolts examined, and the keel re-set. If it looks like this I would suggest finding another boat to buy rather than waste your money on a survey because keel re-sets are very $$$$$$... I would not touch a boat like this with a ten foot pole unless every other item on the boat was near perfect and the owner reduced the price by 8-13k to accommodate a keel reset and the potential for needing new keel bolts.
During survey the bilge should be, and have been, bone dry for a while. The surveyor, if a good one, will use their moisture meter and do spot soundings of the stub. If it has a wood core this can often be identified if it has leaking or is delaminating. If you find signs of moisture in the stub or delam then a core sample can be take to determine if in fact the stub does have moisture or wood in it.
If the stub looks like the one above it can often reveal keel bolts that look like this when the keel is dropped. This can be caused by loose bolts or continued leaking in an oxygen deprived area of the keel bolt or an area where the protective oxide layer has been worn off leaving the bolt unprotected.
Keel bolts in a properly constructed boat with proper keel bolt materials can often go 20 or 30 years without needing torquing. I have torqued keel bolts on 30 year old boats that turned a knats hair and nuts on boats with plywood keel stubs where the torquing to value required more than one full rotation and only served to create a depression in the keel stub as the wet plywood compressed and the fiberglass deformed.
An external keel smile that leaks water or a careful sounding of the stub and moisture meter test will tell you if more exploratory surgery is required. A torque test MAY cause you to shear the nut right off a corroded keel bolt and you can't see this without dropping the keel. No amount of guess work will tell you for sure that a bolt is corroded or not and it generally needs to be dropped to tell. If you damage a keel bolt by torquing then you and the owner are in a real battle...
Personally you would not catch me making the mistake of buying a vessel that had a wood laminated keel stub again. By 1989 Catalina had moved away from wood laminated keel stubs. There are some that are still bone dry but MANY that are wet and rotting.
