Water Pump Impellor

[gordhodgson]

I have a question for sailors with a Yanmar 4jh3 with turbo charger and my case the sea water pump is on the side that is not very accessable although it has the knurled nuts. My question is this once the nuts are removed is there anything that could fall out when I remove the cover and how hard is it to remove the impellor should it slide off easy or will it have to be pried off, remember I will be doing this in the blind cause there is liittle room only enough to get my arm and hand in, also is there a gasket to be replaced or is it a rubber type that can be used again?

Thanks in advance

 

[Steve Dion]

Dancer:

I just put an inspection door in the side of my engine compartment because of this exact situation. I have a Hunter Vision 36 with a 3JH2E engine (assume very similar setup). I have a speed seal with the knurled nuts. Two of the nuts need to be removed and two only need to be loosened (you need to figure out which is which). It would NOT be a bad idea to have a couple extras on hand in case you loose one in the bilge.

You may also want to procure a set of needle nose pliers with a curved nose to make access a little better (and it is only going to be a LITTLE BETTER). There is also an o-ring in there that needs to be replaced periodically. Yours may be slightly different but this is how mine is setup.

 

[Don12364]

It's Not So Difficult

Looks like you have an after market 'Speed Seal' pump plate which has slots for the bottom two holes. These make the task of impeller changing much easier.
My engine is a 3JH2E but has the same configuration of seawater pump. My access is also very limited to the extent that some owners have even cut a hole in the wall of the heads compartment to access the water pump.
I do not feel this is necessary.

First unbolt the alternator. No need to undo the electrical connections because the harness is (just) long enough to allow removal, but you leave it in a position below the mountings. Be careful not to strain the harness.
Next take out the two top thumbscrews but only slacken the two lower ones. Now ease the pump end plate away and lift it up and away.
There is a thin 'O' ring sitting in a circular groove in the pump end face. It should stay in place but if you dislodge it it is not difficult to put it back after changing the impeller - just use a little grease to hold it. Last time I had to raid the galley for cooking fat!
The impeller can now be withdrawn. Remember its vanes are larger in diameter than the pump cavity and are out springing so it will grip inside the pump housing. There is a special tool made to grip impellers and withdraw them. I have never used it but have successfully used two small screwdrivers, each inserted between the vanes on opposite sides at 45° and pressed into the hub without damaging it. Then by levering gently but firmly using the edge of the pump cavity as a fulcrum the impeller can be eased out. Be careful not to score or raise a burr on the pump end face because this will spoil the sealing.
Remember this is NOT the maker's recommended method - their manual is silent on this point and there is no recommended tool. They just say remove the impeller.

Now, to insert a new one, give the vanes a smear of grease and ease it back on to the shaft whilst giving the vanes an anticlockwise twist when viewed from aft. i.e. clockwise rotation of your hand from the front.

Note the Yanmar Service manual recommends checking the impeller once a year or every 1000 hrs running - whichever comes first - but it does not actually recommend changing it - so its up to you.
This is a helpful link:- http://sagaforumet.com/yanmar-manual/4JHE/manual.pdf Just download the index and click on any chapter heading to download the relevant section.
Two extracts from the manual are below.

 

[gordhodgson]

Thanks for the tip with the needle nose and if there was a way of putting an access panel near it I wouldn't hesitate but with my refrigerator right beside it, it's impossible, a mirror placed in the right place may allow me to see it but not while I'm taking it apart, Hunter didn't give a hole lot of thought about maintenance accessability in this case unfortunately.

 

[Allan Frey]

The needle nose you need has to be a right angle, not the usual 45 degree, with about an 8 inch handle. It works quite well.

Bay shore marine in Annapolis, MD sells a needle nose that they heat and bend for use on yanmar engine impellers. A mechanic friend tells me that it works well. See:
http://www.bayshoremarineengines.co...ct_details.asp?prodid=509&source=cat&catid=40

allan

 

[sailingdog]

I'd point out that you shouldn't use PETROLEUM-based GREASE on impellers. Use silicone grease or glycerin to lubricate them.

 

[CalebD]

We replaced the impeller on our Oberdorfer raw water pump a month or so ago. With limited access to the area in our Tartan 27' it was easier to remove the entire water pump (2 bolts) and work on it in a shop environment to replace the impeller. The back plate on our pump has 4 screws vs. 2 nuts to remove entire pump.
YMMV.