For Problem 1
Originally Posted by GJ0KYZ
This is definitely worth checking. If it's offset just centre/center/centaur it up and see if that makes any difference.
"just" centring it will be a bit of a difficult job if it is bolted to the transom! I know of a Ribcraft 5.3 with a 90 sat dead centre on the transom and no pull. My MErc & Yam were both dead centre, again no pull. My money is on your trim tab.
If you are trimmed too far out, the trim tab / skeg etc won't be doing what they should, and you end up with more of the opposing torque at the wheel (Newton's 3rd law - the prop shaft goes one way, so the rest of the engine wants to go the other way with equally vigour, and if there's no water stopping it at the bottom of the leg, it's all down to you on the wheel).
When does it do this? If at speed in a straight line, and it happens at the slightest sign of a wave or a turn you are either trimmed too far out or may have a too small diameter prop.
There are small diameter big pitch props out there for lightweight boats, the idea being that you loose a bit of friction by reducing diameter, and load the engine back up with the relatively high "gearing" of the pitch & get more speed. Thing is if your engine was secondhand off a light boat (As my old Yam was) the prop will let go easily on a relatively heavy draggy rib. You may need to up the diameter & down the pitch if that's possible.
What RPM do yopu get at wide open throttle, and what is your current prop?