RE: Carriage Bolts for F155 Fin
Ummmm I don't think you want carriage bolts!
And for at least 2 reasons:
1st I've never seen 303 CRES (non magnetic austenitic stainless steel)
carriage bolts. They are usually very low grade (like grade 4 or less) steel and some of them are galvanized, some are not.
Might be OK in freshwater, but don't get them anywhere near the ocean.
2nd, a carriage bolt has a large round oval head, with a tapered square locking area under the head. They are made to fit into counterbored holes drilled in wooden planks (the bed or chassis of a carriage or wagon) and have the tapered square pulled down into the drilled hole in the plank to keep the head from rotating.
Not what you need for you F-155 fin at all.
What you need are:
6mm x 1.0 mm pitch slotted hex head or Phillips Pan head (Pozi Drive is OK as well) screws.
I do not see the F-155 on the list, so I'll paste in a couple of 2002 boards that should about the same thickness and use similar length screws.
Formula 136 Deep Tuttle Race 65 M6x1.0 x 45+60mm lg.
Formula 156 Deep Tuttle Race 70 M6x.1.0 x 55+70mm lg.
If the barrel nuts in your F-155 fin are stripped, get a 1/4-20 UNC tap and retap the barrel nuts to 1/4-20 UNC and then get 1/4-20 UNC Phillips Pan Head screws that are:
45 mm = 1.77 in.
55 mm = 2.16 in.
60 mm = 2.36 in.
70 mm = 2.75 in.
I found that Ace Hardware Stores in MN (At least in Worthington) had a pretty good selection of long metric and 1/4-20 UNC screws.
If not, any windsurfing dealer that carries Chinook can get you 6 mm x 1.0 Phillips Pan Head screws up to 90 mm long.
Be sure to get them in 303/304/316 CRES Stainless Steel.
The various head styles, etc. are illustrated in the 2002 Starboard screw thread chart I put together for them at the link suggested above.
Please double check to see if you have a Deep Tuttle box in your board and that the fin is either std. or deep Tuttle. There were a few early F-155's that had std. Tuttle boxers installed at the factory and you could not use a deep Tuttle fin in them.
Many of the F-155's came with deep Tuttle fin boxes and std. Tuttle fins and you would need some longer screws.
If youi have any doubt as to how long the screw needs to be, install the fin and then slide a long nail or pin down into the fin screw hole and measure how long a screw you need.
Don't be afrail to order the next size longer screws as you can easily cut them off and higbee cut (chamfer the imperfect threads on the cut end) them with a hacksaw and a file.
Just be sure they won't bottom out in the fin head below the brass barrel nuts.
Hope this helps,