i had my 25hp merc trimmed all the way in on my yam360 to control the amount of ventilation occouring. what you get with a sib is that as it rides over each wave, the whole boat bends and flexes - this in itself is constantly changing the trim of the engine which causes the prop to lose its grip in the water causing 'wheelspin'. with plenty of practice you will learn your own boat and will know exactly when its about to happen and will instinctively work your engine to suit.
another point on trim is that as a sib doesnt have a heavy or deep hull you have no reason to try to get the bow up - the boat will easily get itself up onto the plane no matter where the engine is trimmed, but in keeping it trimmed in you are compensating for the flex of the boat.
as for tilt mechanism, it should at least have a locking catch to keep it in the tilted up position. this should engage automatically when the engine is lifted.
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