Hi David
I have a 48in Huntsman, an old wooden version and I have fitted a pull start strimmer engine.
The engine just fits in the centre section but you loose the depth of the open cockpit as it ends up being full of engine, I also had to fit the engine backwards (ie shaft pointing to the bow) because there is not enough overall hull length for the engine and propshaft in a traditional setup.
The model sits low in the water but goes like a rocket (60mm prop)
There are smaller 2 stroke engines such as the “Little Wonder” from a hedge trimmer but they are hard to find, some chainsws have smaller engines and they are perfect for a 4ft hull, try trawling through fleabay for suitable units.
Hope this helps
Paul