A permanent mooring for your boat must be far stronger than a simple anchor: Since the boat will often be unattended and subject to winds, tides and possibly severe weather, you must be confident that the mooring will hold your boat safely, under all conditions. Planning and installing a good mooring will repay your effort and expense with peace of mind when the wind starts to blow.
Determine the anchor weight you will need, based on the length of your boat. A mushroom anchor should weigh about 10 times the length of your boat in feet, thus a 25-foot boat should have a 250-pound anchor for severe conditions; you could use less if the boat is in well-protected waters. A 250-pound mushroom anchor has the holding power of a 1,000-pound block of concrete.
Consult a nautical chart to find out the maximum depth at high tide where your mooring will be placed. You will need two lengths of chain: A large diameter bottom chain of 1 1/2 times the maximum depth, and a smaller diameter chain equal to the maximum depth. The smaller chain size depends on boat length: at least 3/8 inch for boats up to 26 feet, 1/2 inch for boats to 40 feet and 5/8 inch for larger boats. The bottom chain can be as large as one inch in diameter.
Connect the large bottom chain to the mushroom anchor with a shackle. Connect the bottom chain to the upper chain with a swivel shackle. Connect the mooring buoy to the upper chain with a shackle. The buoy should be large enough to support the weight of the upper chain. A 15-inch buoy will support up to 27.2 Kilogram of chain; an 18-inch buoy will support 45.4 Kilogram. The chain is usually fed through the bottom of the buoy and attached with a shackle to the top.
Attach a length of line, called a pennant, to the mooring buoy. The length should be twice the distance from your boat's bow chock to the waterline. A pennant diameter of 7/16 inch will work for boats up to 30 feet; larger boats should use a 1/2 inch line (or more). Attach a pickup buoy to the end of this line. The mooring is now ready to be placed in position.
Transport your mooring to the mooring site. The weight of your mooring equipment may be more than your boat can safely handle. If so, hire a larger work boat, preferably one equipped with a hoist, to set the mooring. Lower the anchor first, followed by the chain and the buoy. The heavy bottom chain will pull the mushroom anchor over on its side, allowing it to dig into the bottom over time, increasing its ability to hold your boat in place.
Check your mooring equipment annually. In salt water, mooring chain will corrode and may need replacement every three years or so.