grey alloy props that couldt be welded versus cast aluminium
These days an alloy prop is pretty cheap cheaper than getting welded and re balanced, and that a new prop.
If shallow water, rivers, liable to hit a rock or log, small boats approx 5.5m, under about 1200kg total gross weight on water and general use (not required to pull a skier up or move at high speeds) the loading on a alloy prop and the amount of distortion under that load as to a SS is insignificant.
Its not about the HP of the engine, it is about the load on the prop , a combination of hp and the weight that needs to be moved at cruise or under hole shot if the later is critical to end use of the boat.
Even a larger boat trawling for game fish will not need a SS, thu to move that hull weight to the fishing grounds at reasonable speed a SS would be of some benefit.. In saying that , ideally the prop to get to the grounds will ideally be quite different from that to trawl with.
Funny how they make comparisons between 2 props different cupping, even different diameter . and yeah 1/4" will back a huge difference on smaller boat like that..
Not only that change props , espec significant change in diameter (slip %) means its very likely the engine height needs to be changed as well...