I'm sure they would sell you one.
Or go to the hardware store and buy one. Pretty sure all it needs is for one end to have the eyebolt straightened enough to make a hook.
Then push a piece of hose over the turnbuckle.
They are sold with a hook on each end also.
Lowes
McMaster Carr
Allison XB-21 ProSport
Yamaha 250 SHO
Croxton Razor 4XL
Tractor Supply.
‘17 Bullet 21 SDC ‘20 Merc 300R 1.60 SM 1E081012
Lowe’s and home depot
I recommend stainless steel.
Allison XB-21 ProSport
Yamaha 250 SHO
Croxton Razor 4XL
Here is what I use: standard hardware store turnbuckle with a wingnut added as a jam nut to keep it snug in case of road vibration.
IMG_3949.jpg
A plastic coated cable with enough slack to hook and unhook would be better. If the seat bolts from the winch (which are quite dainty) sheared in an accident, the threads on that little safety hook aren't going to hold in a big blow either. Heck I can flex the whole winch assembly and the upright frame it sits on just walking up the steps. Dare I say, the Boat Mate trailers are marginal in areas. I miss the old Tennessee trailers That all the A boat came with in the early 90's.
I don't use mine.
All the wrecks I've seen and saw pictures of. If it's much of an impact the boats coming off. Even if the winch strap and backup hold---------doesn't take much to break or pull that eye bolt out.