confused about prop test results

[brunolund]

1996 lund tyee 1850, 4.3lx. first prop was SS 21p 3blade, got 4800 rpm and 47 mph. slight bog at takeoff. second prop is SS21p 4 blade- 47 mph @ 5000 rpm( maybe able to go a touch higher, but didnt) much better hole shot, no bog. 3rd prop was SS 23p 3 blade, 47mph at 4400 rpm, then cavitated. hole shot not horrible, but worse than 21p 3 blade. worth it to try 23p 4 blade? and maybe vented? so far happy with 21p 3blade, i just like to play around.

 

[mfkadz]

What's your WOT RPM rated at? If it's higher than 5000 then you have more to get out of it. Mine is 5500.

mike

 

[brunolund]

4800

 

[steelespike]

What hp and do you know the gear ratio? Is your speed by gps?
The 21 and 23 had 20% slip A little high I would think a ss prop would have a little less slip.
Usually low double digits.
I find the 4 blade with higher rpm and higher slip, 23%, unusual? Also 47 mph is also suspicious for all speeds.

 

[brunolund]

speed was not gps, but I have verified speedo is accurate with gps recently. the same speed surprised me too. I got 11% slip when I did calculations. sounds good to me.
my gear ratio is 1.81.
was confused why the 23 was cavitating.? I am happy with how the 3 blade 21 works, except for the slight bog at start. I can live with that though. I should mention both 21's were tested with four adults, and 23 was just two. think I might try a hustler in 23 and see if the vents help the takeoff. thoughts?

 

[steelespike]

What is the diameter of these props?The Hustler is an aggressive prop and could load the motor more than your suspect 23" 4 bld.
It may test like a 24.