You'd be better served if you could borrow a torque wrench of appropriate size. Some tool rental stores may have one, it depends on where you are located.
I work for an OEM machinery builder/ engineering outfit so I have access to one from our shop, usually a 3/4" or 1" drive with the appropriate socket and extension will do. Since Tartan has been in business continuously they should be able to supply the torque spec, if not there may be a resource in one of the owner sites that could help.
I do know that when I rebedded the keel on my previous boat I did it this way and the results were very good. With a large arm on a wrench it's very easy to over torque a bolt. The recommended torque for that keel was 275 ft/lbs, way below the yield rating.
One thing with stainless nuts and bolts is that they tend to seize to each other by galling if even slightly over tightened.
Before attempting to tighten your keel bolts
spray them with some type of penetrating oil
every day for a week or two, then see if you can loosen them before attempting to torque them down. I didn't do this on one boat I owned many years ago and ended up having to drop the keel due to one galled keel bolt, even though I did all the work myself it was a big pain in the ass.
The typical torque for keel bolts
is way below the torque ratings for bolts of that size, the keel bolts are usually sized for load bearing, not due to torque specs.
Again, like one of the posts already stated, only do this while on the hard