Trim is all about changing the propeller shaft's angle in relation to the boat. If your prop shaft is parallel to the surface of the water then the trim is at zero or a neutral position. If it is trimmed all the way down and bottomed out, the prop shaft will be angled down away from the surface of the water. Trim it up from the neutral position the prop shaft will be angled up towards the surface of the water. This will create the opposite effect as if it were all the way down. But what exactly is the trim doing to the performance and speed of your boat in these positions?