Calculating speed...does prop slip change?

[ZmOz]

I'm using this prop speed calculator to see what I can do with a new prop. Since I already know I can do 50mph @ 6000 RPMs with a 19p, that calculates out to 7.3% prop slip. Now, if I get another prop, say 21p, does the slip stay the same?

 

[WillyBWright]

Re: Calculating speed...does prop slip change?

From what I uderstand, slip increases slightly with increased pitch, but it's negligible compared to the hull design and weight. Now that Glastron you have must be a pretty efficient hull. Wish I had one! Is it a Carlson? That 150 loves 6000 RPMs. If I had that and I wanted to go to a 21, I'd definately go Stainless. Probably a Laser. You'd probably only lose a hundred or two. With an aluminum it'd be 3 or 4 hundred. With the added bowlift, a small pair of manually adjustable trim tabs would do you some real justice. It'd help with porpoising. Do you have power trim? With all of the above you could get 56. Maybe a smidge more, but not much more.

 

[walleyehed]

Re: Calculating speed...does prop slip change?

If it's the same manufacture of prop, it may stay close, but if speed is gained, slippage will drop due to less wetted surface in some cases, too many variables to suggest, But I can tell you I've tried to guess at some of my own testing and found it to be oposite of what I thought it should be. Testing and data...the true answer

 

[phatmanmike]

Re: Calculating speed...does prop slip change?

hey zmoz, my 1150 has a ported 21p 3 blade prop, and ive been wanting a 19p prop. hint hint. email me