Re: 3 vs 4 blade -boat lists under full throttle only
Welcome to Iboats.
I don't think a 4 blade prop is going to make much of a difference over a 3 blade.
What does make a difference to stopping list (propeller wise) is either twin counter rotating props (seperate engines), or Duo props (I/O stern drive). Neither is feasible for your situation.
Your list is from simple physics. The boat is slightly rotating on the axis of the prop shaft to the opposite direction of prop rotation.
Sounds odd? OK picture this... If you were to hold the prop shaft still, and allow the boat/motor to spin, it would be spinning to the left. Since the water isn't a solid object, it's not going to get enough grip to spin the boat (that would just be a silly unusable boat), but it does provide enough grip to allow your light weight aluminum boat to be tilted.
This isn't a phenomenon strictly encountered by guys with aluminum boats, and 40hp engines either. It's pretty common to some degree among all boats running a single prop.
You may want to look into upgrading your trim tabs if it really bothers you. A trim tab with a larger surface area would be better to try and stop extreme list.