Probably you have a long shaft engine sitting on a short shaft transom, looking at both pics engine sits too low, water flow hits the upper small plate, where the splash is produced. It's not a prop issue, its' rather an engine/tail height issues.
What you should do is make a large metal plate to sit on transom so to have a stright transom. Would be faster than filling the middle transom cut with wood, resin, fiberglasss ? Check pics for understandig. Water flow must pass under the small water deflector plate, this is the sweet spot, gives best engine top speed, superb performance & impecable tight turns at any water conditions.
This is what you should aim to achieve once engine sits well on transom :