Here's a way to save time and energy when repairing floorboards. Instead of drilling and chiseling damaged floorboards, use a plunge router. First, use a magnetic nail finder to be sure there are no nails in the way. Set scribe lines across the damaged pieces. Then, run the router across the boards for a quick, clean cut.
If vibration causes nuts to constantly work loose, first add a lock washer, if it doesn’t have one. Or, if there is room on the bolt, use two nuts, tightened toward each other so they lock solidly. You can also try wrapping monofilament fishing line under the nut before tightening it on the bolt. Another possibility is to try wrapping the threads first with the teflon tape that is used in plumbing.