Mooring anchor types compared: mushroom, pyramid, helix and granite

Granite or concrete block (deadweight)

A deadweight holds by weight alone. Concrete loses roughly half its weight underwater, so a block's holding power comes from what it weighs once submerged, not what it weighs on the dock. A heavy block is hard to move and works on rocky bottoms where other anchors can't dig in. The trade-offs are size and handling: it takes a barge to set, and there is nothing to bury, so it can't gain strength by settling into the bottom.

Mushroom

A mushroom holds by sinking into soft bottom. Once buried it gains suction as the sediment settles around it, which is why a set mushroom can hold many times what it weighs. It is the most common choice in muddy New England harbors, and any mooring service knows how to set one. Its weakness is the vertical stem: as the boat swings, the chain can wrap around the stem and tighten each cycle. (More on chain wrap here.)

Pyramid

A pyramid anchor uses a short, squat shank to cut down on chain wrap, and it is a common choice in shallow, tidal water. It is a different shape from a mushroom, so it digs in and holds differently, and mooring services size and set it their own way.

Helix (screw anchor)

A helix is screwed into the bottom on a shaft that is typically 8 to 20 feet long, and holds by the soil above its discs. It can work well where bottoms are firm or the mooring has to stay put, and it has little to wrap a chain around. The trade-off is installation: it is usually put in from a barge or by a diver, and the right shaft length depends on the bottom.

MoorSafe

MoorSafe keeps the mushroom's concave bowl and cast-iron base, so it buries and holds like a mushroom, and adds a three-bar cone above the stem so the chain has nothing to catch on. It is set with the same barge, chain, shackles, swivel and pennant a mooring service already uses.

Side by side

Anchor choice depends on the bottom, the boat, the exposure and your mooring service's practice. This is a general guide, not sizing advice.

What we've tested

We've tested MoorSafe against a traditional mushroom only: 300 lb prototypes, side by side. At Yale Cordage in Saco, MoorSafe held to 40,657 lb against 38,560 lb. In a 28-day Casco Bay field test the mushroom broke out at 1,575 lb and was partially buried, while MoorSafe broke out at 1,295 lb and was fully buried. We haven't tested pyramid, helix or granite moorings, so we don't claim results against them. The MoorSafe offered today is the 400 lb. Details are on the test results page.