Re: when i trim up, boat starts bouncing
Hawk;
The Trim on the motor allows you to adjust the bow to stern attitude of the boat. When accelerating from a stop the bow will follow the path of least resistance which is up into the air until there is enough water pressure under the hull to raise the boat to plane. If you note, the transom will have an angle (side view) where the bottom of the transon is further forward than the top (about a 10 to 12 degree rake). This allows the motor to be trimmed down to a position beyond vertical, and tilt the prop up. In this position the prop will try to lift the back of the boat as well as driving forward (not efficient but somewhat effective). Lifting the stern pushes the bow down.
When cruising, and when you attempt to bring the prop to a vertical position (most efficient for thrust) the bow no longer has the upward stern lift to keep the boat from porpoising. In other words the boat is now balancing on an axis which is somewhere near the last 1/3 of the boat. This creates a nice long leverage arm (from the axis to the bow tip) that easily bounces up and down.
The Hydrofoil provided extra stern lift but as the surface are is small, it was not enough. There are many other issues with Hydrofoils, but let's stick to the issue at hand.
Trim Tabs will provide the lift at slow speeds to keep the bow down during acceleration, and will stop the bow from bouncing when underway, thus allow you to trim the motor to a vertical position taking advantage of all of the thrust.
