Smart Trim Tabs Vs. Hydraulic Tabs

Hydraulic trim tabs affect the flow of water around the hull -- called laminar flow -- to maximize the boat's attitude in the water for performance, safety and fuel efficiency. They are controlled by the boat operator. Smart Tabs are spring-loaded flaps mounted on the rear of a boat that cannot be controlled from within the boat. Smart tabs are affected by, but do not affect the laminar flow.

  1. Hydraulic Trim Tabs

    • The boat operator on a boat equipped with hydraulic trim tabs uses them to ensure the hull maintains level movement through the water. Hydraulic trim tabs are operated from the control console or dashboard by the boat's operator. A piston, powered by a hydraulic system much like that of a car's power steering system, moves hydraulic trim tabs up and down. When they are trimmed up, they raise the bow -- the front -- of the boat. When trimmed down, they lower the bow of the boat. Since most powerboats ride with one side lower than the other, due to the torque imparted to the boat by the propeller, there's usually a slight difference in the height of the tabs.

    Using Hydraulic Trim Tabs to Change Speed

    • When the operator trims hydraulic trim tabs downward, they push the bow of the boat down into the water. On acceleration, a slight upward angle on the hydraulic trim tabs can jump-start the process of acceleration, helping the boat rise in the water and minimize drag. On deceleration, an extreme upward angle on the hydraulic trim tabs, combined with an extreme upward change in the tilt of the engine, is useful for an emergency stop.

    Controlling Smart Tabs

    • Normally, you raise hydraulic trim tabs upon acceleration, using the controls on the dash, to help raise as much of the boat's hull as possible from the water. Smart Tabs are different from hydraulic trim tabs. Unlike hydraulic trim tabs, Smart Tabs are spring-loaded in a downward orientation and never rise above a level position, the bow of the boat plows through the water on take-off. At best, the Smart Tabs are forced into a neutral orientation when the boat has achieved sufficient velocity to push the spring-loaded tabs up.

    Smart Tabs Limitations

    • Because the Smart Tabs cannot be controlled from within the boat, the operator cannot adjust them, unlike hydraulic trim tabs. When the boat's speed increases, the tabs remain in a neutral position; hence the Smart Tabs don't provide the same fuel efficiency that hydraulic trim tabs do. Additionally, Smart Tabs cannot be trimmed to level the boat from side to side to compensate for live loads -- people -- that move during the course of the trip. When the operator slows the vessel, he can trim the hydraulic trim tabs up to increase the drag of the boat's stern, decreasing the stopping distance.This is impossible with Smart Tabs, since the operator has no control over the tabs.