Are you talking about through-bolts, or screws?
For through-bolts, best would be to drill, paint the bore with epoxy, then install the bolts.
For screws, drill, insert the screws, remove the screws, inject with epoxy, then reinsert the screws.
Silicone doesn't seem to stand up to the marine environment too well in the long run. Considering what the cost of repairing a rotten transom is, why take a chance?
jky
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