Prop on Yamaha 30hp behind my RIB
Well at the beginning of this summer I had my 30hp 2 stroke 3 cilinder yamaha behind my SIB. The boat was a bit overpowered, the standard prop was damaged, and I had an stainless steel prop with it in the size 10x10. The standard prop was 9 7/8 x 11 1/4.
With the stainless steel prop my engine was reving like creazy (to much) behind my SIB. So I bought an original yamaha prop in the size 9 7/8 x 12. Just to go a little bigger then the standard prop.
I still use this new prop behind my new RIB, which ofcourse is a lot heavier then my SIB. But the hull is far more stiff and better lined, so no energy get's wasted like with the SIB on hi speeds. Hope I said this correct.....
My question now is, how do I know whether this prop 9 7/8 x 12 is also a good choice behind my RIB? The RIB has a total weight of aprox 200 kg and the engine is about 60 kg. Then with fuel, gear and myself with co-driver in the boat a total weight of about 440 kg.
I don't have an RPM meter, so have no idea what rev's the engine is doing, it's all by feeling and sound for me.
The combination now has a topspeed of 27 knots. This is done after testing for the best trimsetting of the engine, since I don't have powertrim on this engine.
Added one pic of the combination with the best view of the prop that I have at the moment.
Any information would be more than welcome!