Water circulation?

[Guest]

Previous to taking my boat out for the winter it had a good flow of water.After changing the impeller i put the hose from the seacock into a bucket of water allas no circulation! Is it possible to put the Jabsco impeller in the wrong way around or will i have to prime the pump ?Thanks for any help.

 

[ccscott49]

the impellor fits both ways, is it a new one. If an old one, they sometimes get worn on one side and tend to lose prime, also how low down is the bucket? the pump may not be able to lift water that high, priming should solve the problem, but it may lose prime again, be careful jabscos' do not like being run dry!

 

[david_bagshaw]

Dont forget a new impeller installed in an old pump takes ablout 20 hours to run in and develop full performance, particularly on suction.

David
www.yachtman.co.uk

 

[byron]

is that a fact David? Well! that is interesting indeed surprising but definately worth knowing.

ô¿ô
www.education-jobs.co.uk
www.alexander-advertising.co.uk

 

[david_bagshaw]

I dont know that it is a fact, but call it ia factoid,

From personal experiance with 10 engines over the last 30+ years & various water systems, macerator pumps etc, and perhaps best of all was discussing my observation with one of Hollands main Vetus dealers, who confirmed my thoughts, indeed thought it was common knowledge.

David
www.yachtman.co.uk

 

[charles_reed]

If all the water has run out of the filter case, and the pump is a little worn, it's quite likely it won't be able to sel-prime.

Have you ensured that you have the impeller vanes trailing in relation to the direction of rotation - it certainly won't work if they are leading.

 

[ccscott49]

Charles, I thought the vanes are straight, (radial) on an impellor always are on the ones I buy!, the upset inside the pump makes them bend.

 

[Guest]

Success, primed the pump today, my wife had to hold her finger on the end of the inlet hose, whilst I filled the pipe down to the pump. When the engine started, she released her finger on the pipe whilst holding it under the water. Worked first time. It was a new impeller and I'am not sure if it went back in the right way! Thanks for all the help.

 

[scottie]

on some Jabsco pumps you can pull the shaft out with the impeller this means that you can damage or disloge the seals when you put the shaft back in
watch you dont push seal back over the tell tale holes as if you do this with some engines you can fill the crankcase
also never put a mains hose direct on to a jbsco or you will blow the seals
and if you are using a bucket dont leave it above the engine or it can empty into the exhaust system and back into the engine in some cases

 

[brian_neale]

Not sure how you tell whether a new impeller is run in or not. Certainly leaving an impeller unused in the pump over the winter will wreck it - the vanes take on a permanent set. I fit a new impeller each year (keeping several new and previously-working impellers on board in case of premature failure - the old Yanmar impeller problem). I grease the impeller blades when fitting, which maybe helps it prime when first fitted. Do not worry about the way the vanes are pointing when you fit the impeller. If you do not believe me, leave the pump cover off, watch the impeller, and turn the engine over. My impeller vanes will all be pointing the right way after about 1 revolution of the pump.

 

[charles_reed]

You'll find that on some (yanmar) the clearance is such that the impeller blades are slightly bent in situ.
It is also possible for the shoe inside the pump to not stariaghten them out again.

All vane type pumps are poor on suction, the slightesy scoring and it drops from about 600mm to 100mm.
That's why waterpumps are usually located low down on the engine (hopefully below the waterline).

 

[ArthurWood]

Maybe not a good idea to use grease on impellere as it might attack the impeller material. Washing up liquid does the trick, but makes impeller v. slippery to handle.