I went to purchase some SS bolts and the supplier only had 304 stainless steel bolts in stock. Are these OK to use for the beam and dolphin striker mounts, or should I try and find these in 316 stainless?
From a structural point of view the advantage of 316 over 304 is so marginal that it doesn't matter. From a corrosions point of view 316 is significantly better so using 304 will get you on the water but 316 will mean you probably don't need to look at the bolts again while you own the boat.