The Fortress FX-37 21LB Anchor is the legendary marine anchor trusted by boaters and experts around the world. Designed for boats in the 46' to 51' range, this anchor delivers world-class holding power without the weight of traditional steel anchors. Fortress has earned its reputation through years of research, advanced materials, and real-world testing—so you get top-tier performance, quality, and value every time you drop anchor.
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Precision-machined aluminum alloy combines steel-like strength with only about half the weight, making the FX-37 easy to handle and store on deck.
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Rustproof and corrosion resistant with a tough anodized finish that stands up to harsh marine environments.
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Sharper design than heavy, dull-edged steel anchors for faster setting and deeper penetration into common sea bottoms.
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Exceptional holding power—designed to set quickly and hold firmly, even in challenging bottoms.
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Disassemblable for simple storage, easy transport, and the option to use as a spare or storm anchor.
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Lifetime Parts Replacement Warranty—free replacement of any damaged anchor part, forever.
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Adjustable 32° to 45° fluke angle—an exclusive feature that dramatically increases holding power in soft mud bottoms.
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Elegant durability with a rugged, corrosion-resistant finish that remains attractive while performing under pressure.
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Perfect fit for 46'–51' boats in Fortress’ model range, with a 21 lb (9.5 kg) weight that balances performance and manageability.
The FX-37 is part of Fortress’ trusted lineup that covers boats from FX-7 to FX-125, ensuring the right balance of weight, hold, and ease of use for your vessel. Its design emphasizes holding power across different bottoms, including hard sand and soft mud, so you can anchor with confidence in a variety of conditions. With the FX-37, you’re investing in safety, convenience, and peace of mind on every voyage.
| Feature | Benefit |
Precision-machined from an aluminum alloy that is as strong as steel, but only half the weight. | - Easy to manage weight
- Rustproof
- Sharper than heavy, dull-edged steel anchors
- Will set faster and penetrate deeper into common sea bottoms for incredible holding power
|
| Can be disassembled | - Excellent as a spare or storm anchor
- Easy to store
|
| Lifetime Parts Replacement Warranty | - Free replacement of any damaged anchor part...Forever!*
|
| Adjustable 32 to 45 fluke angle | - Exclusive and patented feature which dramatically increases holding power in problem soft mud bottoms
|
| Tough anodized finish | - Handsome and durable appearance
- Corrision resistant
|
| FORTRESS SELECTION GUIDE
|
| Model | FX-7
| FX-11
| FX-16
| FX-23
| FX-37
| FX-55
| FX-85
| FX-125
|
| Boat Length |
| ft
| 16'-27'
| 28'-32'
| 33'-38'
| 39'-45'
| 46'-51'
| 52'-58'
| 59'-68'
| 69'-150'
|
| m
| 5-8
| 8-10
| 10-12
| 12-14
| 14-15
| 16-18
| 18-21
| 21-46
|
| Weight | lb
| 4
| 7
| 10
| 15
| 21
| 32
| 47
| 69
|
| kg
| 1.8
| 3.2
| 4.5
| 6.8
| 9.5
| 14.4
| 21.2
| 31.1
|
| Replaces Steel Anchors | lb
| 6-9
| 10-13
| 14-18
| 19-28
| 33-50
| 50-65
| 70-90
| 100-170
|
| kg
| 3-4
| 5-6
| 6-8
| 9-13
| 15-23
| 23-29
| 32-41
| 45-77
|
| HOLDING POWER |
| Model
| FX-7
| FX-11
| FX-16
| FX-23
| FX-37
| FX-55
| FX-85
| FX-125
|
| Working Load
| | | | | | | | | |
| lb
| 700
| 900
| 1.250
| 2,000
| 3,000
| 4,000
| 5,250
| 6,750
|
| kg
| 318
| 408
| 567
| 907
| 1,351
| 1,814
| 2,381
| 3,062
|
| 32 Degree Hard Sand Holding Power
| lb
| 2,800
| 3,600
| 5,000
| 8,000
| 12,000
| 16,000
| 21,000
| 27,000
|
| kg
| 1,270
| 1,633
| 2,268
| 3,629
| 5,443
| 7,258
| 9,536
| 12,247
|
| 45 Degree Soft Mud Holding Power
| lb
| 840
| 1,080
| 1,500
| 2,400
| 3,600
| 4,800
| 6,300
| 8,100
|
| kg
| 381
| 490
| 680
| 1,089
| 1,633
| 2,177
| 2,858
| 3,674
|
| 32 Degree Soft Mud Holding Power
| lb
| 420
| 540
| 750
| 1,200
| 1,800
| 2,400
| 3,150
| 4,050
|
| kg
| 191
| 245
| 340
| 544
| 816
| 1,089
| 1,429
| 1,837
|
| DIMENSIONS |
| Model | FX-7
| FX-11
| FX-16
| FX-23
| FX-37
| FX-55
| FX-85
| FX-125
|
| "A" Shank Length |
| in
| 24"
| 27"
| 31"
| 36"
| 40"
| 46"
| 51"
| 56"
|
| mm | 610
| 685
| 787
| 914
| 1,016
| 1,168
| 1,295
| 1,422
|
| "B" Fluke Length | in | 14"
| 16"
| 18"
| 21"
| 24"
| 27"
| 30"
| 33"
|
| mm | 356
| 406
| 457
| 533
| 610
| 686
| 762
| 838
|
| "C" Stock Length | in | 19"
| 22"
| 25"
| 29"
| 32"
| 37"
| 41"
| 45"
|
| mm | 483
| 559
| 635
| 737
| 813
| 940
| 1,041
| 1,143
|
| SUPPORT HARDWARE
|
| Model | FX-7
| FX-11
| FX-16
| FX-23
| FX-37
| FX-55
| FX-85
| FX-125
|
| Proof Coil Chain
|
| in
| 3/16"
| 1/4"
| 5/16"
| 3/8"
| 3/8"
| 1/2"
| 1/2"
| 1/2"
|
| mm
| 5
| 6
| 8
| 9
| 9
| 13
| 13
| 13
|
| Nylon Rope** | in
| 3/8"
| 3/8"
| 1/2"
| 5/8"
| 3/4"
| 7/8"
| 1"
| 1 1/4"
|
| mm
| 9
| 9
| 13
| 16
| 19
| 22
| 25
| 32
|
| Shackle Size
| in
| 1/4"
| 1/4"
| 5/16"
| 3/8"
| 7/16"
| 1/2"
| 5/8"
| 5/8"
|
| mm
| 6
| 6
| 8
| 10
| 12
| 12
| 16
| 16
|
| NOTE: Hard sand holding power figures above represent loads actually achieved on production FORTRESS and Guardian anchors under controlled horizontal pull conditions without dragging or resulting in disabling structural deformation. ** Rope recommendations are based on 25% of breaking strength. Rope must be in good condition. |
