question

[tertim]

what prop would you run in a mean machine that has a 7xl powered by2- 25c 5000 mh px4s
flowing thru a hydra 240. I am looking for top speed only. I am running the wrong prop right now ( x645 ) and am having a heat issue after extended runs. still able to get over 50 with the gps. I just want some advice from those in the know
Thanks
Tim

[saleens7]

deacreasing the diameter and increasing the pitch seems to work well for more top speed...

[NorthernBoater]

He is at pretty much the highest pitch that is used in FE. What other props do you have. I would try a X640 or X637.

[saleens7]

ooops....misread...though it was x445

in that case, just decrease pitch

[tertim]

I have a x642 I could try. What does it mean when they talk about lifting props???
I am really lost in this area. I have heard that the x445 is a possible match for my setup????

[NorthernBoater]

Try an m545 or m645. The m series will not load the motor as much.

[Fluid]

I am assuming that you are running 4S2P? If so you have too much prop for that motor if you expect "extended" run times. I'd drop down to an x640 or x442, and raise the strut to at least 1/4" above the sponson bottoms, angled up about 2 degrees at the prop end. Set the CG about 9.0" ahead of the transom to fly the boat better. Let the motor wind up and produce some power at lower amps.

I've easily exceeded 61 mph with my MM on 4S with an M440 and a 2800 Kv motor, so it should be possible for you to exceed 50 with your motor and a prop smaller than 45mm in diameter. But you will NOT be able to have extended run times - to get that speed in that hull with just 4S means you have to pull a lot of amps and heat is the by-product. 50+ in that hull for more than a minute or two will require 6S if you want your components to live very long. It is not a hydroplane and has a lot more drag.

.

[steveo]

you dont want a lifting prop thats for hydro and riggers to get the rear end off the water

[tertim]

Poly RC PX4S-5000EX Li-Poly
I am just running short bursts under 30 seconds at this time. just trying to get the hull set up. Thanks for the setup info on the cg. was running a little more that 10" from the transom, will try your suggestion wednesday.
Thanks
Tim

[Steven Vaccaro]

Poly RC PX4S-5000EX Li-Poly
I am just running short bursts under 30 seconds at this time. just trying to get the hull set up. Thanks for the setup info on the cg. was running a little more that 10" from the transom, will try your suggestion wednesday.
Thanks
Tim

In the first post you said "by2- 25c 5000 mh px4s". Does this mean you have two 4s packs in series or parallel?

[tertim]

question

I have them installed where they both go into the esc separtley. I get confused with series and parallel. one battery feeds one lead and the other battery feeds the other lead to the esc. hope that explains it...

[Superveekiller7]

no i think pra220 or 225 has more pitch then x series