Billy Black photo

Harken offers three categories of Big Boat blocks. AirBlocks® are designed for offshore boats where weight and performance are critical. They are lightweight, UV protected and easily maintained.

Megayacht ULC blocks feature mirror-finished stainless steel or hardcoat-anodized aluminum sideplates and our ultralight composite bearing system (ULC) to handle extremely high loads.

ESP, or Elegant Simple Products, is a line of hardware that complements our blocks in looks and function, but is simpler in design and construction.

Big Boat Blocks Q&A


Runner BlockWhat should I consider when sizing a runner block?
You need to match the block's breaking strength, to the breaking strength of the rigging on your boat. If you're not sure of the standing rigging's breaking strength on your boat, check the Typical Rigging Breaking Load chart on the Harken website.

How much does the load change on my footblock as the angle of deflection changes?
Load AngleAs the angle of deflection increases, the load goes up. For example: At 91 kg (200 lb) of load and 45 degrees of deflection, the block will see 76% of the load or about 79.5 kg (175 lb).  If you have a 60 degree bend and 92 kg (200 lb) of load, the block will see 100% of the load, or 91 kg (200 lb). ( At 180 degrees of deflection, the block will see 200% of the load or 182 kg (400 lb). Block loading vs. Angle of Deflection.

I would like to clean up the deck of my boat by leading the line from the mast, aft to the cockpit. I want a block that is low profile, has some articulation, but won't hit the deck. What are my options?
Our family of Teardrop blocks fit your criteria. These blocks will not hit the deck when the line is slacked off, are low profile to keep lines close to the deck, and have sufficient articulation to ensure a fair lead.

Selecting the right padeye for the right Teardrop block can be confusing. Below is a chart showing the appropriate padeye-to-block combinations. Note: when selecting a padeye for a Teardrop block, make sure the breaking strengths are the same. Also make sure the block fits in the padeye loop.

Teardrop-Block-to-Padeye Compatibility
 627 Round648 Round629 Round688 Diamond689 Diamond
6057 X  X
3047 X  X
3050 XX  

What size blocks fit the 598 and the 669 Big Boat stand-up toggles with control tangs?
Harken: stand-up toggles The brilliant thing about these toggles is you can build almost any type of control system. Although you can fasten the tang pin directly into the headpost, it works better to use the shackle. The control block shackle presses into the rubber stand-up to hold the block up. The chart below will help you choose a block that will work in your system. Note: No block should have a greater working load than the working load of the car. Blocks with 8 mm shackles or greater will not work.

Stand-Up Toggle / Control Tangs 598 & 669
40 mm Carbo XXXX 2659, 2149
57 mm Carbo XXXXX2152, 2631
75 mm Carbo X     
Dinghy  063    
2.25" XXXXX 
3.00" XXXXX 
57 mm Black Magic X     
The tangs will not work with blocks that have a shackle 8 mm or greater

I have an older Harken Big Boat Black Magic® AirBlock® that has a broken roller bearing. Can I send it to the factory for repair by a qualified Harken technician?
Although it doesn't happen often, sometimes Harken gear components wear and need to be repaired or rebuilt. In this situation, don't panic! Just pick up the phone and call Harken Customer or Technical Service (262-691-3320), and explain your problem. We will issue a "Return Goods Authorization" number and arrange to have the gear returned to us for repair.

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