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Author Topic: Pumps full of water - Why it happens  (Read 9073 times)

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Offline Painlesstom

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Pumps full of water - Why it happens
« on: October 31, 2012, 02:47:13 PM »
I've talked about how these pumps come in full of water, but just realized I haven't fully explained what I've seen as the cause. The front seal rides on a collar that is slid over the axle shaft. That collar and seals mating areas should have sufficient tension to provide a positive seal, and over time should leave witness marks, exactly like you will see on the pump shaft where it rides in the hull bearing. Without this tension the seal is doing nothing, and leaks are the result. The picture shows an older pump that I rebuilt today, it was full of water too, as you can see the grease milkshake it left behind.

Well used and water filled pump


From the above pump, there are no contact witness marks.


This collar shows the marks my seals made on the test collar I made for my pump during testing last year.

Tom

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Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #1 on: July 13, 2013, 07:39:18 PM »
When you press a bearing into a bore, or onto a shaft, it causes the race to shrink /or expand, which tightens the clearance in the ball bearings. This is called preload, and a little is necessary to ensure the balls rotate and not skid. Mokai has an excessive amount of interference fit in the center axle and that puts too much preload on the bearings, add the drag from the seal on each side of each bearing and that is the stiffness you feel. This generates allot of friction which causes more heat than the bearings are rated for. Severe blistering is seen on the bearings seals on a regular basis. This heat causes pressure to build in the housing, that pressure will burp past the seal. When the housing cools, a vacuum is created like in a preserve jar, this will suck water into the housing. The factory front seal only has a very light contact lip which is no where near enough to keep from leaking. There is a collar that slides over the front of the axle with an o-ring inside to seal it, this collar is what rides inside the front seal. The o-ring doesn't provide a positive seal and is something I address in my rebuilds as well.

My method involves removing the excessive press fit in the axle so as to remove the preload from the bearing completely. The thrust generated by the impeller places an axial load on the balls, which will preload them so they don't skid in the race. I also remove all the seals from the bearing so they are open, which reduces even more drag. The stiffness you feel when you get your pump back from me, will be from my front seals only. The bearings are free of preload, to spin without friction, less friction mean less heat and being lubricated with a housing full of oil means the bearings will last indefinitely. With two double lipped seals, instead of one, and with the right amount of lip tension, there is more than sufficient sealing ability to keep water out, and the oil in. It's an overkill really, one seal with the right tension would be fine.
Tom

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Offline dwshome2000

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Re: Pumps full of water - Why it happens
« Reply #2 on: August 30, 2013, 12:34:34 PM »
What is the result of the pump filling with water?   Extra weight and corrosion?  Does it cause loss of performance as well?

I'm looking at a used boat, and your modification are on my agenda.

Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #3 on: August 30, 2013, 12:49:39 PM »
The water eventually washes the grease out of the bearings, causing them to fail.

Looking forward to helping you out, I'll be waiting to hear from you.  \./8
Tom

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Offline Hunkydory

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Re: Pumps full of water - Why it happens
« Reply #4 on: December 03, 2013, 10:22:42 PM »
For the process of ordering my bilge pump not long ago from Tom, I sent the pump to him for the connection to the pump installation.  When I called to set up the shipping details, he suggested, I also have him rebuild the pump.  I was rather hesitant for him to do this due to it being a 2011 model, not having read this thread & I just found it hard to believe it could already have water intrusion.   Having purchased many of Tom's accessories & always finding him always to be up front & honest in his business, I took his word it would best to be rebuilt at this time.  Well it's a darn good thing I did.  He sent me photos showing the water intrusion & the already compromised bearing from it.  I, as those of you know who have seen my videos, go to some very remote areas with my Mokai, where the loss of the pump could be potentially disastrous, so feel very fortunate to have had him be very insistent that this should be done.  How wonderful it is for us all to have this honest, extremely competent fellow Mokai owner provide this site & the many high quality Mokai improvement accessories he has developed for us.

Jay

Offline Hillbilly

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Re: Pumps full of water - Why it happens
« Reply #5 on: December 04, 2013, 09:19:24 AM »
Jay,
As a great fan of your adventures, I give great respect and credence to your opinions.  Tom has done the same for me - and results have always been good.  Looking forward to new videos from you.

Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #6 on: December 04, 2013, 07:34:36 PM »
Thanks for the kind words guys, it's been a pleasure dealing with all of you. Looking forward to your future videos, Jay. I'm glad I was able to help you out, thanks again for your continued support.
Tom

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Offline Allanlesko

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Re: Pumps full of water - Why it happens
« Reply #7 on: July 07, 2014, 01:26:54 AM »
I have two 2007 model mokai's with the stock 6hp honda motors. I do love my mokai's but have had a lot of trouble with the jet pumps seizing up on me. I sent them back to Mokai and was told stories of bad batches of bearings, bearing supplier did a switch in grade of bearings. The last time I sent a pump to them I ran it 1/4 mile and it seized up on me. I came across this site and saw how tom filled the pump with oil and I figured that is what mercruiser, enirude ect. Have done for years. I was not to sure about sending my pumps to someone off of the internet but I had nothing to loose I had two pumps that would seize up with no warning. I also run my mokai's in crystal clear freshwater. I had both pumps rebuilt by Tom and he was great to deal with. Tracking numbers on shipping and the price was great. I am posting this now because I have had plenty of problem free all day runs on both of my mokai's. I did not want to post a review of how good he is at shipping it's all about how good the jet pumps works and it is great. I would recommend everyone having this rebuild done to your pump.

Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #8 on: July 07, 2014, 07:12:37 PM »
Thanks for the great feedback, Allan. I'm happy to be able to help, and look forward to dealing with you again in the future.  \./8
Tom

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Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #9 on: July 16, 2014, 12:25:42 PM »
Been a busy week for pump rebuilding. This is the worst of 5 I've done this week. If you've been putting this off, now would be the time to have me go through yours. Nobody wants to get stranded with a seized pump. If you're tired of having Mokai replace parts only to have them fail again, my rebuild makes these pumps bulletproof. Just sayin'.....  ;)

Tom

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Offline Ripcord

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Re: Pumps full of water - Why it happens
« Reply #10 on: July 16, 2014, 01:31:00 PM »
I can't imagine being that skilled to go from a blob of molten metal to a perfectly formed spline..absolutely beautiful to see it in pictures. Thank you
"Moonshine ain't nothing but lots of love and goodness distilled into liquid. It will love you like a big woman wearing a straw hat."

Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #11 on: July 17, 2014, 07:37:14 PM »
Thanks, I'm glad you could appreciate it.  :)
Tom

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Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #12 on: December 12, 2014, 05:09:43 PM »
I got a pump in this week from an ES-Kape that the customer wanted rebuilt to my specs. Other than a minor change to the collar seating area diameter, to prevent the axle threads from tearing the o-ring in the collar during installation, there was nothing else different. Same parts, same design, same problems. Oh, the steering nozzle is plastic. Pump had a reported 1.5 hours of use, and it was full of water already. So when you guys decide you don't want to deal with pump issues down the road, I'm still here to provide a Painless solution to the problem.
Tom

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Offline Odie

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Re: Pumps full of water - Why it happens
« Reply #13 on: December 12, 2014, 07:01:26 PM »
Refresh my memory, the new style boat extends the plastic nozzle beyond the stern?

Offline Painlesstom

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Re: Pumps full of water - Why it happens
« Reply #14 on: December 12, 2014, 07:27:16 PM »
The new style boat has the ENTIRE pump hanging out beyond the stern.  :-[

Tom

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