Trim Tabs Sizing Guide
Many factors affect the choice of properly sized trim tabs, and the ultimate responsibility for selection is up to you, the boat owner. To help you decide, Bennett Marine offers you a few guidelines below.
General Guidelines
These sizing recommendations are based on average performance. Your choice may vary based on power, engine configuration, weight distribution, type of boat, and use. The greater the surface area, angle of deflection and/or speed of the water flowing under the trim tab, the greater the lift.
When making a choice between trim tab sizes, remember that the largest trim tabs that will comfortably fit on the transom will be the most efficient.
As a rule, choose at least one inch of trim tab span (per side) for every foot of boat length. (Examples: 22-foot boat = no less than 24" x 9", 36-foot boat = no less than 36" x 9".
Span = side to side measurement
Chord = fore to aft measurement
Whenever possible, choose a 9" chord trim tab, and gain lift through a longer span. The span of the trim tab has more of an effect on the amount of lift. However, a longer chord can be used effectively, and there are situations where you may need to use a 12" chord.
Measuring
Choose the approximate tab size for your boat using this sizing chart. Make sure the tabs will fit your transom using the diagrams below as a guideline. When measuring, disregard the strakes and follow the Vee of the hull.
General Guidelines
These sizing recommendations are based on average performance. Your choice may vary based on power, engine configuration, weight distribution, type of boat, and use. The greater the surface area, angle of deflection and/or speed of the water flowing under the trim tab, the greater the lift.
When making a choice between trim tab sizes, remember that the largest trim tabs that will comfortably fit on the transom will be the most efficient.
As a rule, choose at least one inch of trim tab span (per side) for every foot of boat length. (Examples: 22-foot boat = no less than 24" x 9", 36-foot boat = no less than 36" x 9".
Span = side to side measurement
Chord = fore to aft measurement
Whenever possible, choose a 9" chord trim tab, and gain lift through a longer span. The span of the trim tab has more of an effect on the amount of lift. However, a longer chord can be used effectively, and there are situations where you may need to use a 12" chord.
Measuring
Choose the approximate tab size for your boat using this sizing chart. Make sure the tabs will fit your transom using the diagrams below as a guideline. When measuring, disregard the strakes and follow the Vee of the hull.
| Boat Length | Engine Configuration | Trim Tab Size (spanxchord) |
| 15'-19' (4.5-5.8 m) | Single I/O, Single Outboard or Inboard | 12" x 9" (30 x 23 cm) |
| 17'-19' (5.2-5.8 m) | Single Outboard | 8" x 10" (20 x 25 cm) M80 |
| 19'-24' (5.8-7.3 m) | Single I/O, Single Outboard, or Inboard | 18" x 9" (46 x 23 cm) |
| 19'-24' (5.8-7.3 m) | Limited Transom Space or Extra Lift | 12" x 12" (30 x 30 cm) |
| 20'-23' (6.0-7.0 m) | Single I/O or Single Outboard | 10" x 12" (25 x 30 cm) M120 |
| 22'-27' (6.7-8.3 m) | Single I/O or Single Outboard | 24" x 9" (61 x 23 cm) |
| 22'-27' (6.7-8.3 m) | Twin I/O or Twin Outboard | 18" x 12" (46 x 30 cm) |
| 25'-30' (7.6-9.1 m) | Single I/O or Outboard | 30" x 9" (76 x 23 cm) |
| 25'-30' (7.6-9.1 m) | Limited Transom Space or Extra Lift | 30" x 12" (76 x 30 cm) |
| 25'-30' (7.6-9.1 m) | Twin I/O or Twin Outboard | 24" x 12" (61 x 30 cm) |
| 28'-34' (8.5-10.4 m) | Inboard | 36" x 9" (91 x 23 cm) |
| 28'-34' (8.5-10.4 m) | Limited Transom Space or Extra Lift | 36" x 12" (91 x 30 cm) |
| 28'-34' (8.5-10.4 m) | Twin I/O or Twin Outboard | 24" x 12" (61 x 30 cm) |
| 32'-38' (9.7-11.6 m) | Inboard | 42" x 9" (107 x 23 cm) |
| 32'-38' (9.7-11.6 m) | Limited Transom Space or Extra Lift | 42" x 12" (107 x 30 cm) |
| 36'-44' (11.0-13.4 m) | Inboard | 48" x 9" (122 x 20 cm) |
| 36'-44' (11.0-13.4 m) | Limited Transom Space or Extra Lift | 48" x 12" (122 x 30 cm) |
| 42'-50' (12.8-15.2 m) | Inboard | 54" x 9" (137 x 23 cm) |
| 50'-60' (15.2-18.3 m) | Inboard | 54" x 12" (137 x 30 cm) |
| 60'-65' (18.3-19.8 m) | Inboard | 60" x 12" (153 x 30 cm) |
| 65'-70' (19.8-21.3 m) | Inboard | 66" x 12" (168 x 30 cm) |
| 70'-80' (21.3-24.4 m) | Inboard | 72" x 12" (183 x 30 cm) |