Anchor Selection Guide
Boat anchor size recommendations are for boats of average windage and proportions in 30 knots of wind, average bottom conditions, and moderate protection from open seas. Remember that the loads in 42 knots of wind are twice as much as in 30 knots.
Use three-strand nylon rope, 6-12 ft (2-4 m) of chain and a minimum of 5:1 scope. Also, a minimum of 6 ft (2 m) of chain should be used for every 25 ft (8 m) of water depth. For storm conditions use an anchor one or two sizes larger.
FORTRESS ANCHORS
| Boat Length | ft | 16′-27′ | 28′-32′ | 33′-38′ | 39′-45′ | 46′-51′ | 52′-58′ | 59′-68′ | 69′-89′ | 90′-150′ |
| m | 5-8m | 8-10m | 10-12m | 12-14m | 14-15m | 16-18m | 18-21m | 21-27.1m | 27.4-46m | |
| Fortress Model | FX-7 | FX-11 | FX-16 | FX-23 | FX37 | FX-55 | FX-85 | FX-115 | FX-125 | |
| Weight | lb (kg) | 4 (1.8) | 7 (3.2) | 10 (4.5) | 15 (6.8) | 21 (9.5) | 32 (14.4) | 47 (21.2) | 60 (27.2) | 69 (31.1) |
| Replaces Steel Anchors | lb | 6-9 | 10-13 | 14-18 | 19-28 | 33-50 | 50-65 | 70-90 | 90-100 | 100-170 |
| kg | 3-4 | 5-6 | 6-8 | 9-13 | 15-23 | 23-29 | 32-41 | 42-44 | 45-77 | |
| HOLDING POWER | ||||||||||
| Working Load | lb | 700 | 900 | 1,250 | 2,000 | 3,000 | 4,000 | 5,250 | 6,000 | 6,750 |
| kg | 318 | 408 | 567 | 907 | 1,361 | 1,814 | 2,381 | 2,721 | 3,062 | |
| 32° Hard Sanding Holding | lb | 2,800 | 3,600 | 5,000 | 8,000 | 12,000 | 16,000 | 21,000 | 24,000 | 27,000 |
| kg | 1,270 | 1,633 | 2,268 | 3,629 | 5,443 | 7,258 | 9,526 | 10,886 | 12,247 | |
| 45° Soft Mud Holding | lb | 840 | 1,080 | 1,500 | 2,400 | 3,600 | 4,800 | 6,300 | 7,200 | 8,100 |
| kg | 381 | 490 | 680 | 1,089 | 1,633 | 2,177 | 2,858 | 3,265 | 3,674 | |
| 32° Soft Mud Holding | lb | 420 | 540 | 750 | 1,200 | 1,800 | 2,400 | 3,150 | 3,600 | 4,050 |
| kg | 191 | 245 | 340 | 544 | 816 | 1,089 | 1,429 | 1,633 | 1,837 | |
| DIMENSIONS | ||||||||||
| “A” Shank Length | in (mm) | 24″ (610) | 27″ (686) | 31″ (787) | 36″ (914) | 40″ (1,016) | 46″ (1,168) | 51″ (1,295) | 51″ (1295) | 56″ (1,422) |
| “B” Fluke Length | in (mm) | 14″ (356) | 16″ (406) | 18″ (457) | 21″ (533) | 24″ (610) | 27″ (686) | 30″ (762) | 33″ (838) | 33″ (838) |
| “C” Stock Length | in (mm) | 19″ (483) | 22″ (559) | 25″ (635) | 29″ (737) | 32″ (813) | 37″ (940) | 41″ (1,041) | 45″ (1,143) | 45″ (1,143) |
| SUPPORT HARDWARE | ||||||||||
| Proof Coil Chain | in (mm) | 3/16″ (5) | 1/4″ (6) | 5/16″ (8) | 3/8″ (9) | 3/8″ (9) | 1/2″ (13) | 1/2″ (13) | 1/2″ (13) | 1/2″ (13) |
| Nylon Rope ** | in (mm) | 3/8″ (9) | 3/8″ (9) | 1/2″ (13) | 5/8″ (16) | 3/4″ (19) | 7/8″ (22) | 1″ (25) | 1 1/4″ (32) | 1 1/4″ (32) |
| Shackle Size | in (mm) | 1/4″ (6) | 1/4″ (6) | 5/16″ (8) | 3/8″ (10) | 7/16″ (12) | 1/2″ (12) | 5/8″ (16) | 5/8″ (16) | 5/8″ (16) |
GUARDIAN ANCHORS
| Boat Length | ft | 12′-16′ | 17′-22′ | 23′-27′ | 28′-33′ | 34′-41′ | 42′-47′ | 48′-53′ | 54′-62 | 63′-72′ |
| m | 4-5m | 5-7m | 7-8m | 8-10m | 10-12m | 12-14m | 14-16m | 16-19m | 19-22m | |
| Guardian Model | G-5 | G-7 | G-11 | G-16 | G-23 | G-37 | G-55 | G-85 | G-125 | |
| Weight | lb (kg) | 2.5 (1.1) | 2.9 (1.3) | 5(2.26) | 7 (3.2) | 13 (5.9) | 18 (8.2) | 29 (13.1) | 42 (19) | 65 (29.3) |
| Replaces Steel Anchors | lb | 4-6 | 6-9 | 10-13 | 14-18 | 19-28 | 33-50 | 50-65 | 70-90 | 100-170 |
| kg | 2-3 | 3-4 | 5-6 | 6-8 | 9-13 | 15-23 | 23-29 | 32-41 | 45-77 | |
| HOLDING POWER | ||||||||||
| Working Load | lb | 350 | 575 | 750 | 1,075 | 1,625 | 2,500 | 3,500 | 4,625 | 6,000 |
| kg | 159 | 261 | 340 | 488 | 737 | 1,134 | 1,588 | 2,098 | 2,722 | |
| Hard Sanding Holding | lb | 1,050 | 1,725 | 2,250 | 3,225 | 4,875 | 7,500 | 10,500 | 13,875 | 18,000 |
| kg | 476 | 782 | 1,021 | 1,463 | 2,211 | 3,402 | 4,763 | 6,294 | 8,165 | |
| Soft Mud Holding | lb | 210 | 345 | 450 | 645 | 975 | 1,500 | 2,100 | 2,775 | 3,600 |
| kg | 95 | 156 | 204 | 293 | 442 | 680 | 953 | 1,259 | 1,633 | |
| DIMENSIONS | ||||||||||
| “A” Shank Length | in (mm) | 19″ (483) | 22″ (559) | 25″ (635) | 29″ (737) | 33″ (838) | 38″ (965) | 43″ (1.092) | 48″ (1,219) | 53″ (1,356) |
| “B” Fluke Length | in (mm) | 11″ (279) | 13″ (330) | 15″ (381) | 17″ (432) | 19″ (483) | 22″ (559) | 25″ (635) | 28″ (711) | 31″ (787) |
| “C” Stock Length | in (mm) | 16″ (406) | 18″ (457) | 20″ (508) | 23″ (584) | 27″ (686) | 31″ (787) | 35″ (889) | 39″ (991) | 43″ (1,092) |
| SUPPORT HARDWARE | ||||||||||
| Proof Coil Chain | in (mm) | 3/16″ (5) | 3/16″ (5) | 3/16″ (5) | 1/4″ (6) | 5/16″ (8) | 3/8″ (9) | 3/8″ (9) | 1/2″ (13) | 1/2″ (13) |
| Nylon Rope ** | in (mm) | 3/8″ (9) | 3/8″ (9) | 3/8″ (9) | 3/8″ (9) | 1/2″ (13) | 5/8″ (16) | 3/4″ (19) | 7/8″ (22) | 1″ (25) |
| Shackle Size | in (mm) | 3/16″ (5) | 3/16″ (5) | 1/4″ (6) | 1/4″ (6) | 5/16″ (8) | 3/8″ (10) | 7/16″ (12) | 1/2″ (12) | 5/8″ (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 manufacturer’s ratings of 25% of breaking strength. Rope must be in good condition.
For all tech questions please email us at techsupport@fortressanchors.com and a Fortress Marine Anchors representative will respond in 24-48 hours.