Prop size on a 8XL and Hydra 240 ESC?

[Doozie870]

"Today a club members hydro running a SV27 motor, motor came in at 220 running a x440 2 blade prop."

[kburrows]

Hey guys, after reading this i relized a few people are running a similar setup that i have, I NEED HELP. I got a brand new Hydra 120 and 8xl setup with two 7.2 nicads' 4500s in series and it is very weak. It works but this system barely got my BJ on plain. batteries are live and prop is x642.

Anyone with this problem and how to fix it.

[Steven Vaccaro]

Hey guys, after reading this i relized a few people are running a similar setup that i have, I NEED HELP. I got a brand new Hydra 120 and 8xl setup with two 7.2 nicads' 4500s in series and it is very weak. It works but this system barely got my BJ on plain. batteries are live and prop is x642.

Anyone with this problem and how to fix it.

Ken please start a new thread.

[SweetAccord]

So here is a hypothetical setup (properchopper) if you may advise or anyone:

Boat: SV27
Motor: Fiegao 8XL
Batts: 12 cells of 4600Mha
ESC: Hydra 120
Coarse: None oval corse, simple back and forth straights.

Would the Hydra be underrated for this setup? I know the prop is the last culprit to determine the setup, so what would be the ideal max prop?

[Stealth Assassin]

What Is the smallest prop you guys run? Any 3/16" stub shafts turnned down to 1/8" for smaller blades???

[Mich. Maniac]

Watts = Volts X Amps. I guess I dont get it. If you should only run a feigao 8xl @ 90 Amps then multiply X 14.8 =1332 thats recommended and still over 800 watts they are rated at. So why run more than 120A esc? if you are running period of what prop @ 120A 14.8V you are running 1776 watts. Thats a ton of power and should spin a reasonable size prop. If you are running too big a prop for that then you should chose a larger wind motor with more voltage to increase watts, and or power.

[10gauge]

Thank you everyone for all your input!

I wish I had used a data logger when I ran an 8XL / Hydra 120 / x445 combination a while back - well, I was only 2 months into this hobby at the time. There were other issues I realized afterward which may have contributed to it's demise, but at that time, the boat was running wet, as Ray suggested. In any case, the "sweet spot" for this hull is having the bottom of the strut at least 1/4" above the sponson. Raising the strut has made a huge difference in temps, current, and speed.

Moreover, I think the MM with 2P might be too heavy for a high kv motor like an 8XL, and that's why I thought that the LV240 might be safer. In any case, I have shied away from jinxing a Hydra 120 ESC with an 8XL in my MM and will save my 8XL for a low hull slip design like a hydro or rigger.

I've been recently running a 9XL/4S2P setup where my temps have been slightly warm on everything. Speeds are as follows: m440 = 41mph, x442 = 44mph, and x445 = 48mph. Ultimately I want to hit 50mph with this setup, and hopefully a m545 or a x642 will get me there...