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Old 23 September 2008, 13:27   #1
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why wont it pump?

hi there i have stripped my yamaha 8b down and cleaned the impellor and all the depisits around it and just genrally spruced the area up as it was filthy. before i did this it pumped water fine now it is pumping nothing the odd drip here and there has anyone got any idea why? the tube that sends to the engine is located properly. thanks for any help
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Old 23 September 2008, 13:40   #2
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First make sure the tell-tales not block. Try poking abit of wire in the hole. It could just be debris blocking this hole. It may still be pumping water as the most the water exits via the exhaust.

Second, make sure you put the impellor back in the right way . This happend to a couple of the engines at work (not by me!)
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Old 23 September 2008, 13:44   #3
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Did you replace the impeller? Also check that the vanes are bent the right way.
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Old 23 September 2008, 14:49   #4
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Did you make sure the tube from the impellor housing up to the block relocated when you put the bottom end back on?

Its very easy not to line them up, and the water pump will then pump water into the exhaust chamber not up the tube.

I really think you should have replaced the impellor whilst you had it off, for what they cost, and the fact they should be changed reasonably often anyway, its got to be worth doing.

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Old 23 September 2008, 15:14   #5
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how do i no if the vaines are going the right way? it kinda looked like there were exhaust fumes cumin outa the hole where water was ment to come but that may just have been me.
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Old 23 September 2008, 17:20   #6
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Quote:
Originally Posted by dirtrider212002 View Post
how do i no if the vaines are going the right way? it kinda looked like there were exhaust fumes cumin outa the hole where water was ment to come but that may just have been me.
That would probably be steam, which would imply that you're not getting cooling water to the head. Get the impeller sorted out before running the motor for more than a few seconds at a time, lest you overheat and fry expensive stuff.

Re-read the posts above; the answers probably in one of those.

jky
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Old 23 September 2008, 18:26   #7
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first of all, apoligies for quality of the diagram, but I've had a few kronenbergs

As you replace the impellor ,twist it. As your getting white smoke (blue smoke= normal, white smoke= promblm) replace it so its the opposite way to what it is now. Its pretty simple. Ive had to fix other peoples mistakes before. but while you've got the gearbox apart, you may aswell replace the impeller. If you can find a part number, i have a quantity at work. PM me.
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Old 24 September 2008, 14:00   #8
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you need to make sure that the impeller is turning when the drive shaft turns ,on some models there is a small lug that locates in the slot of the impeller and on others theres sometimes a small peg ,dowel or woodruff key , sometimes they can fall out when re assembling or have rusted away that much it looks like a piece of rust or grit,if its not there the shaft will turn but not the impeller.i have also come across impellers not fitting the shaft properley ie too big or if the shaft is rusty or worn away where the impeller sits which then again stops the key way locating.also impellers wear out on the top and bottom of the blades and not just at the blade tips.
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Old 24 September 2008, 15:16   #9
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first of all, apoligies for quality of the diagram, but I've had a few kronenbergs

As you replace the impellor ,twist it. As your getting white smoke (blue smoke= normal, white smoke= promblm) replace it so its the opposite way to what it is now. Its pretty simple. Ive had to fix other peoples mistakes before. but while you've got the gearbox apart, you may aswell replace the impeller. If you can find a part number, i have a quantity at work. PM me.
All impellors work clockwise as engine does. Once the pump is mounted, turn shaft clockwise with fingers, if mounted properly, should feel some resistance on the shaft while turning. There are some posts on Ribnet for correct impeller change procedures.
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Old 26 September 2008, 15:05   #10
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Right here we go. I went out this evening and i have been back to basics. I have taken the impellor out made sure it is the correct way around i have run just the impellor+gearbox with a cordless drill in a bucket of water and seems to pump water fine. Allthough if i put my finger over the hole where it is pumping water it dosent seem to be coming out at any great pressure and some water comes out the main shaft that travels from the engine to the gearbox, this increases with the more pressure i put on the water exit hole on the impellor housing. Second thing i used my compressor and blew compressed air up the water pick up hose. The air does come out of the tell-tale but it seems to only come out at a fairly high air pressure how freely should air/water flow around the engine when it is not running.
Basically in short do you think that i have a blockage or do you think the impellor and housing needs to be replaced. thanks for your help anyone who is in the know.
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Old 26 September 2008, 17:31   #11
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think i would try a new impeller at least then water pump kit with a new bottom plate ,.can you see if the bottom plate or upper pump case is badly scored or worn .as i said in an earlier post its not just the impellers blade tips that wear its the top and bottom that seal .
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Old 26 September 2008, 18:26   #12
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Try and hook up a water supply to the pickup tube-if there's no blockage you'll get a pee stream. Just make sure you keep the engine upright all the time the hose is connected and you'll be able to start it if you want-but you'll get a stream anyway even if it's not running.

Have you still got the sealing grommet in the impeller housing (if it has one) and if so is it worn enough to lower water pressure dramatically??


Assuming it's OK, go buy all the parts M Chappelow lists. It's a false economy doing anything else on outboards
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Old 30 September 2008, 08:04   #13
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hi there i hooked a water supply to the engine today and it seems to be fine with a strong tell-tale. i also left the engine running fo a while and it seemed fine with no overheating. i put it back together and run it up again. i filled the bucke up with water just below the grommet where u relese the 10mm bolt on the gear shift rod. if i leave the gromet out (lots of noise haha) the engine will pump water not a great deal but it will come out the tell-tale. if i put the grommet back in it just dribbles and seems to be mainly exhaust gasses out of it. im going to track down a new impellor and gasket and housing as thats got to be what it is even though i cant work out why the grommet would make any diference.
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Old 30 September 2008, 13:38   #14
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How deep do you have the engine in the bucket?
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Old 30 September 2008, 16:02   #15
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ive definatly got it deep enough for it to be picking up water. i think its got to be a seal or gasket on the impellor.
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Old 30 September 2008, 16:07   #16
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[ gasket and housing as thats got to be what it is even though i cant work out why the grommet would make any diference. [/QUOTE]

the grommet makes the seal for the water delivery to the engine from the pump if its split or perrished the water wont go up the pipe or the exhaust pressure will try blow the water back down the pump, and if theres any wear on the pump or impeller it makes it worse.
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Old 01 October 2008, 18:32   #17
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Quote:
Originally Posted by dirtrider212002 View Post
hi there i have stripped my yamaha 8b down and cleaned the impellor and all the depisits around it and just genrally spruced the area up as it was filthy. before i did this it pumped water fine now it is pumping nothing the odd drip here and there has anyone got any idea why? the tube that sends to the engine is located properly. thanks for any help
How old is your yammie ? Was it heavyly used ? Is the head been repaired before ?
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