I wanted to let the DIY guys know about the problem I have had with my youngster jet pumps. Much like Simon from RClifeon I had multiple failures with motors, couplers thermal breakers etc. so my jets got very little use. When I finally got everything working I never got speeds even half what Mark was getting. Now I’m a big guy 230 lbs and I am using a beat up SUP so with my weight plus the board and the jet drive plus a big battery pack running it all I was close to 300 lbs. so I was not expecting to be hitting 27 mph like Mark was but I thought 15-18 mph was reasonable. Anyway long story short I never went over 10 mph, then put a buddy who is 150 lbs on the board and he managed 12.5 mph. Ran it again the next day and speed was down to 8.5
Tore the pumps down and found that the impellers were broken, pieces were broken off the stators, the front thrust washer wore almost completely away On both pumps. I asked mark about the failure and was told that I must have done something wrong. He would not give me new parts, then stopped responding to my emails until I started posting comments on his videos to get his attention. Even then he said that he had had no problems nor did anyone else. Since 2 pumps cost $500 and most DIY builders will spend a total of $3000 or more on their jetBoard I wanted to share my experience so y’all know what you are buying. Marks pumps are powerful no question about that but I believe after using MHZ metal pumps and Ypungster plastic pumps that there is a reason you should go with aluminum alloy and stainless steel or ceramic thrust bearings. Here are some pictures of the failed parts. You can see what looks like air bubbles within the plastic which would be a manufacturing flaw I believe, but marks response has always been “ not my fault” so ask about warranty if you buy these pumps and get it in writing 
Hello Frank,
Are you sure that your jets did not suck up any dirt?
As I remember in one of your video’s you mentioned that there was dirt in the pump.
I did damage one impeller but this was because I was doing beach starts.
The beach was full of shells and small rocks!
The bushing at the back of the nozzles are for me fine.
However I can see them getting damaged when running the motor dry to long
I’m a lite person (65kg), and can get my short 190cm surfboard up to around 30 km/h. (on 6P6S)
Funny enough the board got faster when I made it shorter.
Before it was 220cm and no way I was even close to the 30 km/h.
Also. It looks like you placed the jets pretty close to each other. Could this cause your board not to get up to speed as both pumps are sucking water away from each other?
To bad Mark does not respond to you anymore! Maybe your emails are going into his junk box?
Like me. I never check it!
Stay safe! Have fun!
Hey thanks for your response. So as far as picking up debris. The first time an impeller broke ( i have now had 3 fail) Mark insisted that i had to have picked up a stone or stick. I didnt agree but let it go. I have a video of that fail and im in deep water 4/5 feet minimum when the impeller broke so i dont believe its debris but regardless of what caused the failure I think the whole concept of building very high speed jets out of basically plastic is flawed. My MHZ pumps have lasted and lasted. Same boards, same rider weight etc and its not an issue. Im glad your set up is working well. I hope it continues to.
And as for mark not getting my emails He is getting them and lately has responded but only to tell me I caused the failure and his pumps have no problems.
I think the pumps can handle a light rider on a small board but tge load is just too much for them when you double the weight. And thats fine if its disclosed that there are weight limitations… but mark refuses to even consider that my fails are load related so im stuck no replacement parts or refund from mark So not any kind if after sales help at least for me lol
I have dug out the worn thrust washer and i broke off the remaining bits of impeller then used a belt sander to grind down tge center hub of his impeller so that i can slide an alloy 52 mm MHZ impeller onto the shaft and that appears to be working. I have to redo the second jet pump but it dies work pretty well with the 52 mm impeller a bit less power but more than with a broken impeller.
So i will get some use out of the pumps i just wont be buying any more of them ill stick with MHZ they are not that much more than
Youngster pumps and with All the parts Available and a lot of good reliable specs for every pump and motor they sell Not to mention straightforward aftersales support they are my go to supplier now.
If you have any mire insights good or bad as you continue to run your board please post updates. Looking Forward to seeing your new custom board
Yes we did have a look at the MHZ system too before we got Marks jets.
The thing is that (as if with Marks jets) you need 2 64mm MHZ jets to get some “fun” speed.
This will end up way over our budget for the jet board builds!
Have you seen James (the Hacksmith) his MHZ build? He claims he got up to 50km/h with the MHZ, but in the video it does not even look close to this!
One more thing about your impellors.
Could cavitation have caused them to break? Water / air shock waves can do a lot of damage!
And. at this moment we are installing the 120 LED stip in the new je board. It looks so cool.
soon more info about it.
Actually I’m not sure exactly what caused the failure. In my autopsy video I showed where there were air bubbles in the plastic where the blade joined the hub. My jets were the first two he had made in a while and he even said that he had some trouble pouring the epoxy for them. So the failure was most likely a combo of air bubbles in the material, possibly cavitation and also ( from the thrust washer completely worn away ) accelerated failure from the impeller not spinning true and as each piece broke off becoming more and more unbalanced till it was almost completely gone. The point is less that it failed and more that Marks attitude was “ not my fault” without even having a conversation with me and then refusing to accept the possibility that there should be a weight limit to his device. Which is kinda silly, every mechanical device from a bike chain to a seal to a chrankshaft has a breaking point, so his drives have a limit to the weight they can push period. The only argument is what that limit is and instead of trying to find that out or look at my drives to see if it was substandard resin that was full of air bubbles causing the failure, he just shut the door on a conversation that would have benefited us both. I had $2000 and who knows how many hours tied up in that drive and Mark had his reputation and the reputation of some pretty impressively performing jet pumps to protect and he just didn’t want to look too closely at his baby cause he didn’t want to see a flaw. Every builder that buys these jets is gonna spend the same $2000 I spent or more and some will have no issues and some will struggle to get the thing to work. If mark wants to sell these jets he needs to accept the flip side of that coin and that is a dissatisfied customer who wants his money back or wants some part or repair under warranty. That’s the expectation when you buy pretty much anything here in the US . If Mark won’t accept this reality he needs to advertise (In Big bold type) that there is no warranty no refunds no replacement parts free of charge period. That way people who are about to drop $500 or more with him followed by $500 for speed controllers and $350 for motors and $50 for remote and $500 for batteries etc etc understand that they are on their own.
I was a damn paying product tester. Every fail I had I reported back to mark and within a day he was making a video of the issue I brought up. He even had some of the same problems that I had and he never tried to warn me that a motor was not powerful enough or whatever the issue was he just let me make the mistake and I kept reporting back to him. But the day I realized the impellers and stators were cracked and chipped and that the thrust washers were worn away and that I had resolved every issue with the drive yet it was failing badly… he just stopped responding to my e mails. So if you want to spend $500 of your hard earned money on these jets with that kind of service, knock yourself out I’m sharing an expensive year long project failure to make everyone aware of my issue, so you can be better informed before you buy.
On the speed that dude claimed he got there is no way unless it was a jet 80 that he was making 50kmh. I would argue with you on the fact that you think you need 2 jet 64s to have any fun on a jet board. I have gotten a 11 ft paddleboard go 9 mph or 141/2 Kmh using one jet 52 so I think on a board that is designed to be powered by a jet drive ( or two) so shorter with a flat tail , wide and thick for lots of volume should be good for 30 Kmh min with 2 jet 52’s and for me in the us they come out to about $700 for both shipped to me versus $500 for joungster jets , I’ll take the slightly more expensive jets that have an all metal construction and lots of. Parts available, plus a tech page with specs on every part they sell and customer service if you have a question . Yes I’ll go with MHZ until there is some players in this market that provide the same or better products sor the same or cheaper prices and that also offer knowledgeable customer support they are the only jet pump supplier that I trust .
Apologies for the long winded response but I posted originally to educate buyers and this thread makes little sense without the back story if my build.
Cheers Frankie