My genoa winches sit on a stainless steel right angle that thru bolt all the way through the inner and outer layer of fiberglass with 3 carriage bolts with no support in between the layers of fiberglass. I think the .25" bolts are 4" long.  If your bolts only go through the inner layer, then it sounds like you need to invest in 6 carriage bolts. I can't imagine your current setup being strong enough for a large genoa unless you were to beef up that inner part of the bulwark with say a stainless steel backing plate.
Peter

Paul:

I have added the block in between the hull and the deck for the winches. With the bolts going all the way through all three.

My boat like yours, had the winches only using the deck for support when I bought it. (I noted some small stress cracking from this) = not good at all.

For the fix I took off the winches looked into the bulworks and fitted a couple of 4"x 6" x 1.8+/-" yours may be other than 1.8"thk. from below (I cut or sanded down the thickness part) and pushed the blocks up in there (mostly tight), then I pulled them back out used a bit of acetone to wipe the area clean for the bond and then added 1 layer of wetted out 8 oz glass 8"x 6" over the top of the wood, then shoved it all back up into the space and had a stick to prop it up, just in case it wanted to slide back down (Use a bit of wax paper under this mess when pushing it up into position, it will drip! the wax paper helps with the mess.  Lastly with a long drill bit I bored from the existing holes in the deck out through the wood and then through the hull as true to square as I could.

I used longer ss carriage bolts to rebolt the winches.

One note for Peter: if you do not add the wood and glass in between, you are trading the 5/16" glass of the deck for the 7/16"+ thickness of the hull.  I.e. if you do not put a spacer in, you do not get the strength of both.  This is what will happen when a core delaminates, or what would happen if you took out all of that bracing on a truss style bridge.  Just a FYI your setup is only twice as strong as the original through the deck only bolting, but If you install the block, the bolts are the limiting strength issue and should = about 12,000 +lbs +/- so, if you use 7/16  or 1/2" line, the line or the sail (will break first).

Dave a note on the turning block it sees 2 times the line load. This is true of all 180 deg blocks.  

     sail pull        <------------
                                   O ) -----> load on turning block = sail + winch
      wench pull   <------------

Norm    

Please Note: I do love paper towels they are great!, and when doing glass work, always check that I have a full roll at hand before mixing the epoxy, some how I am always happier if I remembered to have the paper towels near when working with sticky dripping stuff.

Jay that is a nice picture:

I have to use a turning block off the boom gallows for my drifter; but the setup in your picture would not require this (Nice).  And I agree totally that your layout makes the cockpit a nicer place to be!!

But from an engineering point, the turning block could have very big loads on it. Example if your jib sheet had 3500# tension on it, the turning block would need to hold a load of 7000#, if it is using ball bearings, this load may start to crush them depending on mtl & size.  So just watch how much you load up the sheets and check those blocks often for ware and for movement.

Engineering aside, I do like your layout, just be careful on the loads.

Norm

p.s. just in case you wanted to know; my routing uses a standup block just aft of the grate on the side deck as close to the bulworks as  possible.  Engineering wise = ok 3500# on the line = about 800# lifting on the block. but it is kind of in the way+/- but the feed to the winch is fine.