Originally Posted by ian parkes
Does engine size and the number of propellor blades etc have any standard .
I have noticed most bigger engines I see have a 3 blade prop but my little Honda 20 has a 4 blade .
Is it worth changing props , i presume Honda have just fitted a good alround prop for the 20 engine . Is there a way to get any advantage with a different prop considering the engine is pushing a small SIB .
They tend to put 4 blade props on small engines to get more thrust at slow speeds - for example when using the engine as an aux on a yacht.
A 3 blade will give you a higher top speed(or should).
My 15hp suzuki has a 3 blade prop which pushes my 3.1m at about 20 - 25mph. When I use the engine on my rib I may get a 4 blade for more low down thrust.