Just got back to this- was out sailing yesterday. I like to do MA calculations the way I would for a block and tackle. Fin*Din=Fout*Dout. So for the bolt and conveniently say a 1 ft wrench on the bolt, one full turn with 100 lbs (so the torque is 100 ft-lb) would be 100*2*pi*1 ft=628. The bolt has a pitch of 8 per inch (I think it might actually be 9 but it doesn't matter), so in one full turn Dout=1/8 inch =0.125in=(.125in)/(12in/ft) =0.01 ft

so 628 ft-lb=Fout*.01, divide both sides by .01 and Fout=62800 lb.

A few interesting things here a) the bolt diameter never came in b) it assumes a frictionless twist. You could have put the equation entirely in terms of "bolt diameters" as units (of course the force at the bolt radius is greatly multiplied so 100 ft-lb at 0.44 inches is 2727 lb at the bolt radius). As to the friction, these bolts are dry, so I would assume a worst case scenario of 0.1 or 90% goes into friction and our answer would have been 6280 lb. Anyway you can find calculators on the web that work all this math (adding in pitch angles, tensile strength etc) and you end up with a simple relationship:

T=c*D*F where T is torque(in-lb), c=0.1-0.2 (friction), D is the bolt diameter (in), F is force (lb) [now the pitch is gone!-darn math]

This equation gives the answer 14000 lb.- only about a factor of 2 off of my simple minded approach (hmm maybe I've misplaced a factor of 2-sounds like a diameter/radius thing? might also be in the friction definition- close enough though)

Ok now let's turn to preloading... Preloading is black magic, but I would argue here that the bolt that CY used was not a complete POS- let's say grade 2. That bolt has a dry torque spec of 165 ft-lb with a net clamp force of 11400 lb [hmm somewhere in between the two] - this is at 75% of max, so 110 ft-lb has margin even on a grade 2 bolt (higher grades are much better). So the difference in preloading 600 lb of dead weight on each bolt can easily be compensated by a 10% increase in the torque applied . In reality, most torque wrenches are only good to 20% (or worse) and the friction term is uncertain at 50% level, so I doubt this 10% matters much.

All that said, I'd rather be on the hard when snapping a keel bolt than in the water!