Hi Green!
There is no single best answer to your issue…just reasonable options…
Typically a limiting factor with chains ans shackles it the minimum diameter of either the chain link or the shackle pin or collar.
So if a 3/8 diameter shackle pin doesn’t fit the chain one wants to ask the question as to the actual chain link material diameter…
The next aspect is if the chain material is actually 3/8” diameter and the shackle pin is 3/8” diameter then it should fit… right?
Well sometimes when the chain links are made there is a ‘weld’ which can cause a bump that reduces the open space restricting the shackle pin insertion. There are a couple options in that case ….
—> One is to file down the link bump (generally ok for SST but not desired for galvanized).
—> A second is to reduce the shackle pin to fit (generally ok for SST but not desired for galvanized).
—> A third is to expand the link diameter with a taper drift enough to fit the shackle pin. (This is generally my preferred option if that is possible as it minimized the removal of any galvanizing and SST doesn’t care… the only caveat is you don’t do this option with forged ling chain as it will result in potential cracking of the link).
—> A fourth is to use an appropriately sized splice link that fits both you chain and your shackle pin .. This is a sorta spiral open link that one threads in to the last chain link and squashes together or has a riveting feature to close. (Personally I’ve used this approach over the years but I “derate” the assembled system by 25% to 50% as under extreme load conditions I have seen splice links unwind themselves.

)
—> A fifth option is to look at your actual requirements vs. perceived needs.
How much anchor holding capability do you really need?
Windward side of a rocky shored coast during Hurricane Gale Force 8 levels or just a calmish on lake lunch?
A slow moving creek or last ditch before getting to the edge of Victoria Falls in Monsoon season?
With 2200/8800 lbs for 3/8” vs 1100/4400 lbs for 1/4” a valid argument can be made for making the choice to goes with what fits as one could reasonably see that the 1/4” shackle could be sufficiently strong enough for one’s needs short of anchoring in excessive weather, wind or current conditions. If you are planning on contending with extremes then you’re gonna need to get a different chain that has a sufficiently large enough opening to fit the 3/8” shackle pin.
Our personal system is limited by our deck cleats which I personally figure is ballpark limited to about 1000-to-1500 lbs max or there about.
This is just an estimated experience based best guesstimate of the 20+ year old assembly of two 3/16 diameter threaded bolts into 1/4 inch-ish fiberglass backed by washers and nuts are what holds a fwd deck cleat in place and that no matter how you do it in reality only one cleat at a time is gonna be holding or taking up the load.
So, for us anyways, the limiting factor being the deck cleat determines what the capability of the rest of the anchoring system.
Going much beyond that limitation isn’t gonna buy us anything beneficial.
Our baseline is that if we are ever
forced into something exceeding that capability we will admit that we screwed up on our problem avoidance measures (not getting into the situation in the first place) and are going to deploy our secondary anchor system to share the load to backstop the primary one.
Personally we’re fully committed to avoiding problems and conditions if and wherever possible.
Having weather apps on our phones and checking the conditions prior to and while out let’s us know what to anticipate and where we need to go to stay out of trouble.
Having a GPS chart plotter with up to date charts backed up by phone app maps/charts and a spare (ancient) GPS handheld lets us know where we are and where we can head to.
Having a good reliable engine on our Mac26X should allow us to get to where we need to be… but this is our primary propulsion as we’ve been using our boat as a cruiser. Our mitigation for this is diligent maintenance and situational awareness to avoid any situations where the loss of power can become a critical problem and not merely an inconvenience. (While we do have a TowBoat membership they still take time and logistics to get there.)
If extreme weather is predicted for our area we take the appropriate precautions such as doubling our fenders, slip dock lines and springers or just go ahead and haul out with our trailer.
Hope this helps with your decision making on which direction you choose to go with in resolving you anchor setup.
Best Regards
Over Easy



