Got it! I saw the motor trying to be a submarine, but it wasn't clear about what was going on to make it do that.
The pics show the motor is WAY too low in the water while underway. One or a combination of a couple of things are likely responsible. First, that's an older pontoon with small tubes. The weight of that motor is causing them to float lower than they were designed to float. Second, the engine pod design isn't carrying the motor high enough in relation to the tubes. The sides of the engine pod, which extend up to the flooring cross members, is too tall. The fact you already have the engine mounted on the transom with the cavitation plate even with the bottom of the pod means there is no room to lift the engine any higher. If you try, the bottom of the pod is going to screw up the water flow to the prop, causing further issues.
I think mom is right. A different boat (with larger tubes that can handle a motor that size), or a smaller motor, are your better directions.
Last, there's a good reason you don't see 6 cylinder engines on a regular pontoon often (nearly always on a tri toon). It's their weight. A 4 cylinder is about max. Something under 350 lbs or so is about all you can get away with on the newer/bigger tubes you see used in production on the newer boats. That kind of weight, as proven by your pics, will nearly always overwhelm an older boat with smaller tubes.