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
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