HOBBY KING Jet pump

[Punisher 67]

I have always been a huge fan of jet drives but have yet to ever build a boat with one . As soon as I seen Hobby Kings unit for $369.00 I had to buy one to check out . I had dreams of building a 3080 powered jet boat and I figured this pump was certainly man enough to make it happen .

Three weeks after ordering the pump it arrived and I didn't waste any time unpacking it - the initial observation once it was unpacked was WOW awesome job .......but my excitement was short lived . Right off the bat I noticed how rough and sloppy the shaft felt - and the how sloppy the steering and trim assembly at the front were .

( The good )
Being curious with the interior workmanship I took the whole unit apart down to the last bolt , the machining on all of the crucial parts , The housings front and rear , The pump rotor , The pump stators and The steering & trim assembly were absolutely beautifully machined . I am no expert on how a great impeller would look like compared to a good one as far as efficiency but it was very well machined and almost perfectly balanced .

( The bad )
The shaft machining , bucket bushings and final assembly was obviously done somewhere else , To my surprise the shaft support on the front of the pump was just a cheap brass bushing unlike the bearings at the rear .

( The ugly )
The shaft was so poorly done that it would of taken out the seal and front bushing on the first run leading to a catastrophic failure , The buckets were so loose and sloppy with there crappy aluminum bushings that the steering would have been sketchy at best and hard on the servo gears .

( The fix )
So what do we do - We have this diamond in the rough and it certainly needs some correcting . This pump has great potential but absolutely needs some alterations . The first thing I did was copy the original stainless steel shaft to a lot tighter tolerances and re-machine it in Aluminum for mock up purposes until I either made my own stainless steel shaft or just farmed it out and get the professionals to do maybe a small batch run and sell them to all the other unfortunate owners in the same boat as me . Doing some reading on the jet pump forums confirms that they are all done this way .

Bearings - The front bearing I settled on a 6mm ID x 15mm OD x 5mm thick ceramic unit , Next I centered the stator housing in the mill and made sure I was absolutely positively without a question centered cause being out as little as 10/1000th's would put the blades into the housing and once I was spot on I pocketed out the 15mm hole . The rear bearings were adequate but I figured I might as well go ceramics through out . The dimensions on them were 8mm id x 22mm OD x 7mm thick and there are two of them in the rear .
And finally the the steering and trim assembly , I settled on 4 ceramic 8mm od x 4mm id flanged units for a really smooth up , down , left and right movement . The holes were drilled out to 8mm and the bolts supplied were very close to 4mm .

I used the old aluminum bushings as spacers for the bearings but had to machine them a bit for a perfect fit , After reassembling everything I got drunk........No just kidding...... . I sat down with a few brews and started brain storming on connecting a motor to this pump

[Punisher 67]

More pictures

[oscarel]

That is a beautiful pump. What size boat is it going in?

[Punisher 67]

This is the second part of the Pumps picture story and the step by step machining and merging to a Lehner 3080 motor and one of the brews that helped me think.....

[Punisher 67]

More pictures

[Punisher 67]

And some more

[Punisher 67]

and a few more

[Punisher 67]

And finally the last of them

[Punisher 67]

That is a beautiful pump. What size boat is it going in?

Thank you........Check out the boats here - they are very good candidates I figure and to answer your question it would be the 1100mm in the model range .

http://www.jettec.co.nz

[HydroMike]

Sight won't load

[srislash]

That was worth checking out.I may be wanting to talk to you about these jets Punisher.We do some jet boating in Vancouver as we have lots of creeks.Something bigger than an NQD would be nice. Here's some of ours http://www.youtube.com/watch?v=05_3BeWBBXU

[Punisher 67]

Sight won't load

It loads ok at this end Mike - try now I dropped the slash

That was worth checking out.I may be wanting to talk to you about these jets Punisher.We do some jet boating in Vancouver as we have lots of creeks.Something bigger than an NQD would be nice. Here's some of ours http://www.youtube.com/watch?v=05_3BeWBBXU

I will try to help where I can - I liked your video - tough little boats

[ray schrauwen]

Wow, thats allot of work you had to do to get it up to standards. Nice job, can't wait to see the full project.

[siberianhusky]

Thats cool! I'd have to stick it in a scale patrol boat river (PBR), Apocalypse Now live at the local pond! If I remember right you'd need two of them though.

[srislash]

Thats cool! I'd have to stick it in a scale patrol boat river (PBR), Apocalypse Now live at the local pond! If I remember right you'd need two of them though.

Two of them would add up $ wise.Sure would be a cool boat though.

[sundog]

Punisher, thanks for your review of the HK drive - very informative. Your mounting 'cage' being in direct contact with the water (through the intake grill) should transfer a bit of the motor heat away as well (water cooled mount). I am anxious to see it installed and running in something! I'm a fan of the jet sprint hull - great handling boat design and much fun in the rapids, too. Bravo!

[FighterCat57]

I wonder if two of these would do OK in a 60" MTI Cat, since there's so much sponson space?

Would have to machine the pickup to match the sponson bottom, but would be a very cool twin jet.

[Punisher 67]

Don't hold your breath guys this will be a slow build up I have still yet to decide on a hull .

[sundog]

I wonder if two of these would do OK in a 60" MTI Cat, since there's so much sponson space?

Would have to machine the pickup to match the sponson bottom, but would be a very cool twin jet.

I can't say, as I've never seen it done before (heard a lot of opinions, though). I have seen a couple of mini monos with stepped hulls that did fine, as well as a mini no-step cat that also did well. I have to admit to having reservations about using jet drives on stepped hulls. I've always thought aeration might cause priming and cavitation problems at higher speeds. But maybe not, still waiting for someone to try it!

[Old Sloppy]

@ Fighter Cat 57


I think two of HK jetpumps are overkill in a MTI, think of "Jet-SAW" racing............
I have two Pletts in a 60" SuperCat (similar to MTI) and that is way overkill...2 3080's = 4 Pletts........

Harry

[ray schrauwen]

@ Fighter Cat 57


I think two of HK jetpumps are overkill in a MTI, think of "Jet-SAW" racing............
I have two Pletts in a 60" SuperCat (similar to MTI) and that is way overkill...2 3080's = 4 Pletts........

Harry

What KV are you turning on those Pletts?

[Old Sloppy]

the HP370BM50 A1s is 813 kv

[ray schrauwen]

Thank you. I'm going to use a pair of 880kv T600 outrunners in my 41" on 9S.

[mgriggster]

Punisher, did you make extra shafts for this? I am one of the unfortunate people who bought one of these pumps too and see what you mean about the shaft. I would love to purchase one if you had extras made. I bought a jet sprint boat from Davette boats and he is assembling it for me. I sent him the pump and he pointed out the issue with the shaft. He said it was undersized and the bearings didnt even spin so your just running metal to metal. Let me know if you had extras made as I would love to have one.

[Punisher 67]

Hello mgriggster

I tried to machine one out of stainless steel and did not a bad job but ended up sleeving the bearing part with some brass tubing cause I overshot a bit on the diameter - its a good fit on the bearings but maybe a bit of blue locktight would ensure no slippage , the second one I machined was out of aluminum and that one fits great but I question its strength on the long haul . I will eventually machine another out of stainless steal but have to buy some special carbide indexable bits and I don't know when that will be . You can have the first one I made its certainly better than the one you have .

P/M me your addy and paypal me $7.50 for postage if you want this shaft .


It really pi$$es me off that the pump itself was beautifuly machined and then they farmed the shaft out to some backyard fumblef*ck operation and to boot put a cheep bushing at the front in the stator housing , this can be a great pump if they didn't cut those corners . I ended up machining in a bearing boss for my stator and replacing the bushing with a ceramic bearing - that upgrade makes this roll so smoothly . I can do that for you also if you mail me your front housing .

[Old Sloppy]

Ray Schrauwen,
Do out-runners like 29,200 rpm's ?
If no then try 8s for 25,950 rpm's
or 7s for 22,700 rpm's
this is based on 3.70 volt lipo's
Harry

[Heterodox]

Just bought this pump and a Scorpion 7050/340 to happily mate for an experimental commercial project.

I was planning on running through the pieces and making the aforementioned improvements, but I've got other projects that are pressing me for time and my machining skills / available tools are lackluster.

I'm wondering if you might take my entire pump and bestow the same love upon it? It should arrive from HobbyKong next week and I need it tweaked before the end of the month. PM?

[100 mph jet boat]

Any updates

I just found this thread and im into real jet boats and would love to see this build

[Punisher 67]

This will be a winter project for me I just do not have the time right now to finish this - I am working 12 hour days sometimes 14 days straight - work right now is stupid busy

[100 mph jet boat]

at least your working... {:<)

will be looking for some updates this winter {_o__@__o_}

DSC_0014.jpg