King Marine

                                67 Acre Avenue, Barrington, RI 02806

                              (401) 247-KING (5464)


What is a mooring?


A mooring is essentially a permanent anchor. It consists of three major parts: ground tackle, chain, and the pennant float/line. There are several different options when putting together a mooring, each which has its benefits and drawbacks.

When choosing ground tackle, there are several factors which must be taken into account including, but not limited to the type of bottom where the mooring will be placed and depth of the water. A mushroom type of mooring is generally well suited to muddy bottoms where the depth of the water is greater than eight feet. This is because a mushroom gets its holding power by digging into the mud, and not necessarily the weight of the anchor itself. A general rule of thumb for mushroom weight is approximately 10 lbs per foot of boat in a protected harbor. When set properly, mushrooms typically take 2 years to settle into the mud for maximum holding power. However, because it is generally less cumbersome than other mooring options, it is generally the easiest mooring to install for the "do-it-yourselfer".

Unlike a mushroom, a pyramid style, cement block, or other weight such as a railroad wheel, rely primarily upon weight to develop holding power. Over time, a cement block or weight will develop suction on the bottom; however, this typically takes a number of years on a hard bottom. We often recommend this type of ground tackle in the Narragansett Bay area because they will work both on muddy and/or hard sandy bottoms, and because these weights are lower profile.  You don't have as many concerns about the depth of the water and boat bottoms bumping the ground tackle. Also there is less of a chance of the chain wrapping and tangling on the shaft. One thing to keep in mind is that if you choose to install a cement block for your ground tackle, you will require much more weight to get more holding power as cement loses approximately 30% more weight in the water than steel.

Another option for ground tackle is a toggle or helix screw type of anchor. One advantage these have over other mooring set-ups is instant maximum holding power; however, there are several drawbacks. First, installation and maintenance of these types of anchor is more time consuming and labor intensive. They are much more difficult to relocate in the event small adjustments need to be made; for example, if two boats are hitting or should you purchase a larger boat. Second, it is more difficult to inspect the ground tackle (bottom shackle and gear). Third, there are only a limited number of service providers who can install and relocate these types of moorings. And finally, they are not currently accepted by all local towns as a valid mooring anchor.

The midsection of a mooring consists of upper and lower chain, shackles, and swivels. The thing to keep in mind is to understand the heavier the chain and more scope of you use, the more holding power you have. Local regulations dictate minimum requirements for chain. However, typically boats less than 40' will use 3/4" chain for lower chain and 1/2" chain for upper chain. Shackles are needed to connect the ground tackle, lower chain and upper chain. When choosing a shackle, select the shackle that is one size above the chain size. Finally, we recommend you use swivels on all moorings as this will help eliminate twisting, thereby shortening scope and decreasing holding power. It also reduces uneven wearing of the chain over time.

The final section of a mooring is the upper portion which consists of the mooring float, pennant line, and if desired a mast buoy. Mooring ball design and size can vary, and recommendations are made based upon depth, current, and size of the boat. There are also different types of pennant lines. The two main types of line include three strand nylon and braided lines. The three strand nylon is the most economical and commonly used. Nylon works well for pennant lines because it stretches more, thereby dampening the pull on the mooring. There are additional options to consider when putting together a pennant line such as using Y bridle, double pennants and chafing guard. Finally, a mast buoy is an accessory that some people like to have because it can make bringing your mooring up on deck easier.