NQD jet boat up grade need help

[wparsons]

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Nice edit... too bad my email notification had the original.

Read the thread RCU, there's lots of discussion about the efficiency of the drive and what rpm range to stay in.

Most jet drives, even the very nice KMB ones, are happiest in the low 20k rpm range. Their 28mm drive says to stay around 21k.

I'm not saying higher rpm won't work or will ruin the drive, but you aren't getting any gains out of it by revving it faster like you would with a surface driven prop.

Mine is absolutely no faster from 3/4 to WOT but it definitely makes more noise and revs higher.

[C.B.R.]

Since you quoted me in your post, I assumed you were talking to me. I have read the ENTIRE thread on RCU. I don't agree with all of it, it is a collection of other peoples opinions. I chose to build my boat the way I wanted to, not to be a sheep and do it they way everyone else said to do it. I have 2 videos in this thread of my boat running, I don't see a problem with it.
But I did not do everything I was supposed to do according to the trolls on the RCU thread. I have a 5000mah 40c 2s lipo (was told it was too heavy), a 25a ESC (was told it wasn't enough amperage), and a 4800kv 4020 motor (was told it was too many RPM's).
But it seemed to work anyway.

http://www.youtube.com/watch?v=Tt4GF-QkNmc

[sundog]

Trolls? People offer advise and you refer to them as trolls? You won't get much help from here with that attitude, bud. They said 5000mah would slow that boat down (versus a 2000mah) because of the weight, not that it wouldn't work or fit. You were probably told the 4800kv wouldn't last on 3S, not 2S (preferred with that motor). And that 25A esc won't last long from my experience - you have been lucky so far. But your luck is running out here.

[C.B.R.]

Like I said, I havent ASKED for any help. I am always given answers even though I don't ask for them. Just like your entire post just now. That is all "your experience".
I done with this, going to drive my boat that doesn't work and leave the technical stuff to you experts.

[wparsons]

Since you quoted me in your post, I assumed you were talking to me. I have read the ENTIRE thread on RCU. I don't agree with all of it, it is a collection of other peoples opinions. I chose to build my boat the way I wanted to, not to be a sheep and do it they way everyone else said to do it. I have 2 videos in this thread of my boat running, I don't see a problem with it.
But I did not do everything I was supposed to do according to the trolls on the RCU thread. I have a 5000mah 40c 2s lipo (was told it was too heavy), a 25a ESC (was told it wasn't enough amperage), and a 4800kv 4020 motor (was told it was too many RPM's).
But it seemed to work anyway.
http://www.youtube.com/watch?v=Tt4GF-QkNmc

Like I've already said multiple times, I'm not claiming your boat won't work. What I am saying is that more rpm won't make these boats any faster, you can't argue with facts. I've seen my own boat first hand and other videos where they don't pick up any speed, just more noise, with more rpm. If I had a 2s 2200mah pack I would make a video of back to back runs with mine, and I bet the 3s pack isn't really any faster than the 2s pack. 2s on my motor is still ~27k rpm unloaded, which is more than the drive is happy with. I know for a fact it would run much cooler as well on 2s, and probably get more run time. If I were to build another, I would either run 2s or go with a lower kv motor to keep heat down and reliability up.

Your motor on 2s is the same (exactly the same oddly enough!) rpm as mine on 3s so I would bet that you don't really gain any speed (just more RPM and noise) between about 3/4 throttle and full.

Here's mine on a 3s 2200mah pack, the slow cruising parts are about 1/2 throttle and the WOT blasts are pretty obvious:

http://www.youtube.com/watch?v=lpTvhV-zU_E

[sundog]

Like I said, I havent ASKED for any help. I am always given answers even though I don't ask for them. Just like your entire post just now. That is all "your experience".
I done with this, going to drive my boat that doesn't work and leave the technical stuff to you experts.

LOL, the idea is that we can share and benefit from others' experiences so that you don' t make the same (sometimes costly) mistakes. But I understand your need to learn for your self. No worries, Sdg.

[NQD1]

What did you use for the water pickup?

[NQD1]

What did you use for the water pick up? Did you just use a peice if metal tube or did you order a special peice?

[wparsons]

I just used a short length of brass tubing (1/8" I think), cut at about a 45 degree angle on the end inside the pump outlet, and epoxied it into place.

[NQD1]

Ok thanks how far does it stick down into the jet?

[wparsons]

Ideally as little as possible, but it needs to be in a fair amount to function.

[NQD1]

Thanks! You guys are great quick response and lots of help!