If the engine has electro-hydraulic power trim, the basic rules for adjusting the trim angle are as follows:
To plane the boat, the trim should be adjusted all the way down (negative setting: “bow down”).
When the boat is planing in low waves, the trim and bow should be raised until the boat starts to porpoise, the propeller loses grip or the engine reaches the upper limit of the normal adjustment range. When this happens, lower the bow slightly until the ride is stable.
When the boat is riding into waves, the bow should be lowered until the ride becomes smooth.
When driving with a tailwind or driving into very high waves the bow should be raised slightly to avoid ploughing through the waves.
Do not drive the boat at high speed with a fully negative trim angle (bow down) as this may cause the boat to roll from side to side and make steering unstable.