yeah what hull?
I have a 8XL under 14,4V with a K42 (1.65 dia. but only 2.28 pitch) on a 36" hull and pull 68amps constant and 76amps burst!!! I have a cheap Mystery 80mp esc with watercooling mod that work just fine but close to over heat!!!... I know the 8xl is not appropriate for such a big hull!
I would go for a 100 (small hull) or 120 because of the 2.64 pitch of the 642!!!
I run my 8XL in a 12-cell Sport Hydro racer, and with an m440 prop I am as fast as anyone else in the club. The x642 overheated my cells in a 90-second heat. Speed is ca. 50 mph - it will be lower in a cat. Don't overprop a BL motor.
The Hacker70 is too small to take the loads you are giving it for long. One club member just replaced his H70 because his boat had slowerd down. He put a Castle 240 in it and the boat is much faster. The Hacker 70 was slowly going away - he had been using an 8XL and x640 prop in a P Sport Hydro.
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I tried a 642 on a 8xl with a hacker 70 on 4s in a p sport hydro before, the hacker is toast the hull is black and I ended up owing my dad 200 bucks. I personaly wouldnt try it again.
I tried Jays setup on 4s 8xl m440 hydra120 and hit 55.6mph on the gps, I also tried a bigger prop on it gained very little speed and a lot of heat.
In my limited experience with FE, big props cost money.
The 120 is fine, try an M440 prop as suggested by Jay, and tune the boat to match the prop.
I am a newbie myself, but my hydro went from 44.3mph on gps to 55.6 on gps, both these speeds were on an 8XL m440 prop, my biggest speed gains came from CG placement and strut setting, not prop.
Jeepers I am building a bby ss hydro will be using 8xl m440 hydra 120. Am very interested to hear about set up of strut and CG. Any info I can get at the moment. Sorry to steal your post Tunda
Hey TUNDA, I think you should not run that set up, its to fast, might be like "woah whoa, whatch it whatch it.....zzzzzzzzip crash!!!! right into the orange Vee.
lol hehehe
I would run a 9xl. it has more torque than the 8xl which allows some room for mistake. For example if the 9xl is not enough rpm, but plenty of torque you can prop up. But if the 8xl is not enough torque, but has the rpm, you have to prop down. Its better to prop up slightly in most cases.
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