yanmar 3ym20 johnson water pump rebuild

[greeny]

Water pump dripping, got the parts delivered now and about to strip out for rebuild.
I know that at some time in the recent past I've seen a guide with tips to doing the rebuild and I'm sure it was on the forum somewhere. I've tried searching but can't find the post I'm after. Can anyone with a better memory point me in the right direction please. I'm not really concerned about starting the job without the guide but I seem to remember that there were some good tips that would be useful and it would be silly not read it again and avoid any pitfalls.

 

[VicS]

I dont recall the post you mention but there is a YM service manual at http://www.motoren.ath.cx/Download.php?filename=/yanmar/3ym-2ym-service-manual.pdf which might be useful . (Page 159 et seq for the seawater pump)

 

[greeny]

I dont recall the post you mention but there is a YM service manual at http://www.motoren.ath.cx/Download.php?filename=/yanmar/3ym-2ym-service-manual.pdf which might be useful . (Page 159 et seq for the seawater pump)

Thanks Vic, it's not what I was looking for but no doubt will be handy for the future. The exploded diagram on there has raised a question though, it only shows one seal on the shaft and I've been supplied with two "oil" seals. No doubt all will become clear when I strip it down.

 

[ghostlymoron]

I did mine a while ago and it had 2 seals back to back. The inner one seals oil from the engine and the outer seals water from the pump. They're both the same and should be fitted with the lip towards the liquids. Make a note of the orientation when dismantling the old ones. Some don't have stainless springs and won't last long! Also check the spindle, if its worn, replace it. Press the seals in with a suitably sized socket preferably in a vice.

 

[VicS]

Thanks Vic, it's not what I was looking for but no doubt will be handy for the future. The exploded diagram on there has raised a question though, it only shows one seal on the shaft and I've been supplied with two "oil" seals. No doubt all will become clear when I strip it down.

If its a belt driven pump as shown in the manual there will only be one seal. If its mounted on the engine and directly driven from within then there will be two seals as GM describes.

Odd that that there is this discrepancy / variation for the same engine but there you go. Actually I dont think GM has a 3ym20 in his Mirror Usually they have a VP MD1

Check the bearings too!

 

[alan]

Have a look at YOUTUBE, there are some videos on there, not particularly for that pump but they give some good guides as to how to get bearings on/off. You will need to mark where the bearings need to go on the shaft and press them on from the "corect" direction so as not to score the part of the shaft where the seals sit ...... that is if you are replacing bearings. When I re-built my pump a few months ago, I found that the bearing on the "salt water side" disintegrated when I tried to remove it - presumably damaged by water getting past the seal. Worth doing the bearings whilst when you are in there!

Alan.

 

[greeny]

Thanks for all the input. I have managed to find an article on doing the job on a similar pump (volvo) which has given me more information but is not identical. It suggests replacing the springs in the seals with correctly sized o rings to stop the corrosion issues so I may do that if my o ring kit has the right size rings in it. I'll also look on u-tube before I start and see what it's got to offer.
Vic, I think you're right - my pump is belt drive so will only have one seal not two.
Anyway, I've got 2 seals, 2 bearings, a new shaft and new impellor. Hopefully I won't need anything else.
Just need to find the time to get to the boat and get started.

 

[ghostlymoron]

Yet another accidental deletion - IS IT ONLY ME? AAAAAAARGH
What I said was
Sorry chaps, I should have read the question as my erstwhile maths teacher used to say. I was describing what I did on my md1 engine which is direct drive and not belt drive. This has 2 seals and no ball bearings.
One tip for the Opie is to examine the seals that have been supplied and reject them if they don't have stainless steel Springs. Suitable sales are on easily available from any bearing outlet and can be obtained with stainless Springs.