The C-clamps are quite secure but heres a recomendation. Get one of those locking bars that goes over the T shapes tighteners, or a padlock if you have the type tighteners that have a hole for that purpose. The reason is two-fold. First is that many seem to loosen from the vibration of being on the trailer driving to your favorite river and the second is so that the motor is still there if you stop for a quick bite on the way home. Only people I know who use the bolts are those that permanently mount kickers on their sleds and don't plan to remove them.