I have recently purchased a lightly used 1992 Hunter 33.5. The boat has been on the hard for about 2 years. She was surveyed 3 months ago with a few things to fix. It was advised to torque the keel bolts. I contacted Hunter Marine service and got the torque specifications fo rthe bolts based on size. My boat has 7 x 3/4 and 1 x 3/8. All went well until I go to the forward most bolt. It snapped off at the floor of the bilge. This nut on this bolt held the bonding plate to the keel. It was in bad shape. I did not want to go through the time and expense to drop the keel to fix the bolt or drill another 3/4 hole and tap it for a new bolt.

I hogged out around the broken stud to a depth of 1/2 into the floor of the bilge, cleaned the threads and installed a 3/4-10 x 1 1/8-12 thick walled SS insert with a large pattern flat washer and nut. The insert was bedded in place with 3M 4200. The bonding plate was cleaned and relocated to the top of another keel bolt using SS HW and SS external tooth lock washers.

The broken keel bolt was rotted at the electrical junction. There was a high build-up of corrosion at that spot. About 90% of the bolt was rotted away. The remaining bolt was ground down to new metal before installing the insert. The insert was torqued to the 3/4 bolt specification. It is unknown if the bolt rat was caused by lightning strike (unlikely but possible) or electrolytic corrosion (most probable).
The steel keel was mostly exposed with some scale and flaking. The keel was ground to bright metal and painted with 2 coats of interlux Primocon 360R underwater metal primer, 2 coats of interlux white 2-part 2000E barrier coat and 2 coats of West Marine CPP antifauling paint.