Noland, the keel was drilled and tapped to a depth
of about 4". The threading was course, maybe 20 x 3/4. The keel bolts were spaced in pairs with two pair before the mast
, two at the mast
step, two aft of the mast and two under the engine
. Try to back out at least one keel bolt to verify the diameter and thread spacing. Manufacturers tend to go with the same process so your keel likely was done the same way. Verify before you get far into it. You do not want to retap cast iron if you guess the wrong size with your clean-out tools. Somebody makes a tool to back out bolts with a drill. I don't think that would work in your case. The torq required is just too much.
One other thing, you may also have two bolts under your engine. You really will not be able to do much with them unless you lift
the engine off the motor
mounts. On the other hand, since most engines drip oil
, those two studs may be in okay shape. If so, just replace the bolts and washers.