3 blade prop slower then 4 blade ?

[ahicks]

Yes, my bad, yes you did say that. I missed it.

But now I also see you're basing your results on results with just one of the props running at WOT. The fact you had to dial back on the throttle to keep from over revving the 3 blade pretty much invalidates your test.

If you were running a 3 blade and a 4 blade, both with similar blade styles, and both absorbing 100% of the engines power, then you would have a fair comparison.

If both props were turning 4800 at WOT, running under similar conditions, THEN you have a fair test.

How would you expect the 3 blade test to compare when you are not running full throttle with it?

 

[porscheguy]

From what I see on the turning point website, the hustler 3 and 4 blades use different blade geometry. The three blade appears to use 3 Mickey Mouse ears, and the 4 blade appears to use 2 MM ears and 2 “cleaver” style blades. They also make one with 4 cleaver style blades, but I don’t see one with 4 mm ears.

As a rule, they also say when you switch from a 3 blade to a 4, you should also step down in pitch. But this rule assumes that you’re properly propped with a 3 blade. You’re data clearly shows you’re underpropped with the 3 blade. But it shows you’re correct with the 4 blade. Try a 21P 3 blade, see what you do, then, adhering to the old rule about reducing pitch when switching to a 4 blade, see how it compares.

 

[jimmbo]

One thing I have noticed regarding TP brand props. I have opened several boxes on the shelf and 50% of the time not all of the blades have the same shape. Running my fingers along the face of the blade I would feel a change in pitch or rake, but not on all the blades. Currently they are the least expensive prop on the market, less than $100(can) for a prop that fits 150hp and higher OB or I/O. However the price reflects the quality and perhaps the results. I know what props work well for me. I only wish I could find a 2 blade, I figure that would give a higher top end, with some loss of hole shot. Or there might not be enough blade area and it will suffer blowout.

 

[ahicks]

This goes back a hundred years or so, but for those interested, I ran a 2 blade on a 70hp Merc "Tower of power" when they first came out back in the 60's. I think they have a very notable vibration to them. The one I did anyway. When I went to a 3 blade, vibration was gone, but so was 2-3mph.

 

[porscheguy]

One thing I have noticed regarding TP brand props. I have opened several boxes on the shelf and 50% of the time not all of the blades have the same shape. Running my fingers along the face of the blade I would feel a change in pitch or rake, but not on all the blades. Currently they are the least expensive prop on the market, less than $100(can) for a prop that fits 150hp and higher OB or I/O. However the price reflects the quality and perhaps the results. I know what props work well for me. I only wish I could find a 2 blade, I figure that would give a higher top end, with some loss of hole shot. Or there might not be enough blade area and it will suffer blowout.

The turning point hustler, dual geometry prop does have 2 different blade types. 2 Mickey Mouse ear blades, and 2 “cleaver style”. I won’t comment on their quality as I have no experience with them.

As for 2 blades, although they can be faster, the downside is vibration.

 

[jimmbo]

I actually learned about the 2 pair props today when at the dealership, I went behind the parts counter and logged onto TPs website. The props I was mentioning were 3 blade props. I have no interest in 4 blade props

 

[HT32BSX115]

Why stay with an under performing 4 blade?

I went from a 4 blade to a 3 blade that improved my hole shot while increasing my top end speed.

I went from a 20p 3 blade to a 26p 6 blade and lost a little speed but the hole-shot is now spectacular!
(actually not a 6 blade but 2--3-blades turning in opposite directions)