Long time follower,new member. Prop recommendations does not seem right?

[ktoy442]

I have a 1996 Mariah 220Z with a 350 alpha 1 1.62 ratio. For the most point I am happy with the performance. Wot 50.3 gps at 4600rpm running a stilleto 3 blade 19p prop. I am considering a 4 blade since we mostly do watersports with the kids. I called turning point prop and they recommended a 17p 4 blade. I know nothing about 4 blade but I was assuming a 19p 4 blade would be a better choice. Is it common to drop 2 pitch sizes when going to a 4 blade? I am struggling with why I should get a 17p over a 19p 4 blade. I am not opposed to a drop in pitch in a 3 blade but had a 18p that was cavatating if I raised the outdrive a little bit. Just looking for a little better holeshot. Thanks for your help

 

[Scott Danforth]

yes, its common to drop in pitch when adding blades.

 

[dingbat]

Generally speaking you drop pitch to make up for the increased resistance of the 4th blade.

Be aware that all props are not created equal. Switching prop between makes and models can be a crap shot.

Case in point, Stiletto props have a lot of cup and a number of them are ported. A prop of the same pitch from a different manufacturer may or may not perform the same because of these characteristics.

I would be inclined to use an on-line prop selection tool to see what they come up with and go from there.

 

[ktoy442]

The online selectors are putting me in a 15p prop which I know is not correct. I get the drop in pitch for the 4th blade but then a high five prop recommends same pitch that you are running in a 3 blade. How can 5 blades not require a pitch drop but 4 does? I appreciate your replys

 

[dingbat]

The online selectors are putting me in a 15p prop which I know is not correct. I get the drop in pitch for the 4th blade but then a high five prop recommends same pitch that you are running in a 3 blade. How can 5 blades not require a pitch drop but 4 does? I appreciate your replys

As I noted above, props have number of characteristics that define prop performance beyond pitch.

This articles explains some of these factors and their affect on performance.

https://bblades.com/props-101/

 

[ktoy442]

As I noted above, props have number of characteristics that define prop performance beyond pitch.

This articles explains some of these factors and their affect on performance.

https://bblades.com/props-101/

Great article, thanks for sharing. After reading that article, I feel as if I need to do an exchange prop program or be content with what I have. Thanks again