Re: Turbo TXP on a sport's cuddy
Gunner, I am having some problems understanding the actual statistics on the boat and prop, and you know me and my programs need exact information to ever analyze anything. LOL
In your original posting you say it has 25 degrees of deadrise and in a later posting you mention that it is 21 degrees of deadrise, and also in your original posting you mention getting a Turbo TXP but later on you talk about a turbo txp ot 4 at 23" pitch. So I assume that you actually meant the OT 4.
You mention that you are able to get 55 MPH at 4,000 RPM out of the new Turbo prop with 8% slip and the 21" pitch Black Max gets 51 MPH at 5,000 RPM with a 23% slip and finally the 19" pitch Mirage Plus gets 50 MPH at 5,000 RPM with 15% slip. And in my opinion the Turbo TXP OT is the wrong prop anyway. I ran some numbers for prop slip and came up with a little bit different slip than you did. I also looked up the Turbo prop at their site and here is the information that they give, I intend on calling them later today and see If I might get lucky and get a different person than you did and get a more accurate analysis on all of the prop geometry in this prop. And what is the RPM range for that motor, I couldn't find that
But here is what their sight says about this prop.
Faster hole shots and quicker acceleration, through the use of an over-and through-hub exhaust design which helps the engine develop RPM rapidly. Very aggressive pitch, high rake angle, large diameter and more advanced trailing edge blade cupping makes these props excellent for ?surface piercing? applications. Excellent high-horsepower, high-speed propeller for very light, high-speed boats, particularly those using high engine mounting heights or a hydraulic jack plate and having naturally greater bow lift ?built-in?.
By their nomenclature I am thinking that the (aggressive pitch) possibly means progressive pitch,( but it could just mean high pitch) and it has a high rake angle and the trailing edge cup adds a lot of stern lift.
1. Progressive Pitch helps Accelerates Better because it has multiple pitches which helps the acceleration and yet produces a Good Top End
2. Progressive Rake has the most Bow lift available with good speed, great holding power at high speeds and Rough Water and less cavitation and ventilation
3. Trailing Edge Cup will add Stern Lift, acceleration and theoretical pitch and reduces ventilation as well as increases speed but does lower the RPM
But I see that they don't make this prop in anything smaller than a 23" pitch, is that going to be a problem, I mean will they take it back and give you your money back or at least let you trade it for something else from them. That would mean that we need to figure out which other prop they have that might be suitable for your boat, and that would restrict your options some.
I also was wondering if the sterndrive is mounted higher than normal, like some of the other faster boats.
It did bother me that you said you were getting a porpoising effect at about 50 MPH with the new Turbo prop and that is not a good sign, as you well know. Neither of the other props have that same geometry, lifting both the bow and the stern, and that is where I see this is one of the main problems with this prop for your boat. I believe that high rake angle is what is causing your trouble with that porpoising.
The Black Max, if it's model number 48-78112-21 has a Regressive pitch as well as 16 degrees of rake in the 21" prop and if its model number 48-16312-21 it has Progressive pitch and 20 degrees of rake.
I do not have the stats on the Mirage Plus, and the standard Mirage is a heavy load pushing prop according to Kenny, but the standard Mirage has 16 degrees of Parabolic rake.
H
