Cutting Down Prop Diameter

[Tamelesstgr]

Guys,

If I take a prop that is say 47mm and cut the overall diameter down to 45mm, does that cause any major issues to the effectivness of the propeller? I swear I read a thread around here about this topic but I'll be darned if I can find it.

Thanks,
Ken

[NativePaul]

It will have less thrust for a given speed, so you will get more prop slip.

I have cut down several props with both good and bad results, some have been bad for the intended boat but good for another, and vica versa.

It is possible that it was on the edge for your boat, and it now cavitates horribly, needing more throttle for a given speed, heating things up more and reducing runtime, accelerating slowly, loosing top speed, or even not getting it up onto the plane.

It is also possible that it had plenty of thrust to spare, and it now draws less amps lowering temps and increasing run time, can still accelerate as hard as the hull can cope with, gained more RPM from the lower load than the extra slip cost so increased the top speed.

Unless it is a RTR where dozens of people have the same hull and electrics (and even then it will vary with setup), I doubt anyone can give you a definitive answer on how it will effect your boat. Try it and see.

[Tamelesstgr]

Thanks for the response, that all make sense to me. One example is an Octura Y547. On my 26" mono it's too big. I had tried a 48mm prop on that hill and it torque steered horribly. This hull likes 42mm mostly, it will run a 45mm ok. Thought it could be cut down to 45mm, but I may just sell the big ones and look into some TFL or ABC props.

[kfxguy]

Just get the right prop for it. 442 or 642 and be done. Sell the props you have that don't work or that you don't need. On my 26" mono I run a CNC 443 or an abc 1615 when I want to go fast. The abc does cavitate a bit until it gets on plane. It goes like 55 with the CNC and 64 with the abc.