rib help

can any one help i have a avon sea rider 4meter rib
i have put a 40hp marina outboard on it
the first time i tryed it as soon as i put the throttel on it listed bad to the left
slow speed it was ok
so i put the trim on the last hole and it was ok but the boat is running flat
and not getting the bow out of the water
i was told to raise the engine one and a half inches and one and a quater to the left i did this and it made no change can u help please i used to own this rib 6 years ago and had a 35hp on it with no probs many thx bill

 

i had the same problem with a 4meter Flatacraft i had, with a 50hp Johnson. if you werent careful it would pull hard to the right in my case, so you had to hold onto the steeringwheel at all times. ironically, i had a 35hp engine on that before too and it didnt give any problems.
I found changing the prop helped though. But i didnt have it long enough to actually work out why it did it. i put it down to the engine just being to much for the short hull, and the prop torque was throwing it off.
the fact it does it at speed, and not off the plane makes me think it is torque from the prop, and at slow speeds the hull is gripping the water and there isnt much torque, but when you incrase the throttle, the torque is to much for the short hull, and on the plane means only the back few feet are in the water, and the prop is throwing the boat to the left. Shifting the engine over slightly might help, it shouldnt be perfectly centered anyway, to counteract the prop torque, but if you tried that and it still does it then thats not the problem.
id try changing props. maybe try a smaller pitch, or smaller diameter. You might sacrifice some speed, but might make it more stable. id say its the prop at fault, maybe the leg is bent, or the prop is damaged. can you hold it striaght by steering right?