Would it be a good idea to remove all of the nuts or remove them one at a time to clean the threads before torquing to insure an accurate reading?You can a torque wrench from any number of sources, Sears being a good one. However, be aware that whatever torque values you find for your size keels bolts and nuts is for Clean and Lubricated fasteners. Just tightening them as they are, in a generally semi-corrosive environment, where they have likely been untouched for years, will not give you anything like an accurate reading.
Yep. A cheapie will do just fine, actually better than the expensive clicker which will be more easily affected by corrosion. It is actually a tool you should have aboard if you ever have to do engine work. As in torquing any set of bolts, take 'em up little by little, alternating as you go. Agree that being corroded will not allow a good torque reading so get some PBS Blaster and free them up if possible before tightening.One at a time - you can do that in the water.
This is an instance where a cheapo torque wrench will be plenty good enough. Many, many keels have been tightened with nothing but a wrench and a long piece of pipe "until the suckers screamed".
Keel bolts aren't a situation like the main bearings on an engine where very precise torque is critical. A cheap wrench will give EVEN torque on the bolts, even if it isn't accurate to the Ft. Lb.
On the other hand, this is also a perfect situation for rented tools.