raw water pump

[ex TL systems 63]

Hi got a yanmar / johnson raw water pump on a 3ym30 motor that seems to be worn in the body / cover plate ie impellor is new but the brass body is worn so likely needs a new pump complete. Anyone know if these can be rebuilt or is it cheaper to replace the whole thing at 600 or so. Seems if there was a liner available it would be as good as new again?

[Steve Pope 243]

replacement prices of these pumps are horrendous, maybe a time to look on line? Had a look on Amazon, there was one for a volvo 350? $180.00 US.

[wheels 543]

Yes these pumps are stupid expensive and the Kits are stupid expensive and the cost of repair by some repairers are stupid expensive and I really don't know why. I go to Auckland Bearing supplies and they sell me the bearings and seals for...depending on pump, usually $35 to $65 dollars. It takes 10 to 15 minutes to replace them. I have done the job for a couple of Crew'ees now.
When it comes to wear in the pump body, usually it is the end plate and the cam thingy that bends the impeller blades. I replaced the end plate on my pump last year and the plate cost me about $60 from Lighthouse over Albany direction. But I think that was trade price.The overall pump body should be OK.

[ex TL systems 63]

By end plate do you mean the cover plate that gives access to the impellor? That has some wear and the pump stopped pumping mid Tasman. We turned the plate over and faced it with some plastic which gave a nice smooth surface for the new impellor to rub against and the pump started working again but will not always prime.The pump works fine if you pull off the outlet hose to get water flowing and then put it back on again, I think there is too much clearance at 1 point from the tips of the impellor blades to the pump body and air travels past there.Seems if there was an option to get a slightly oversize impellor that would solve the problem, either that or I wonder if I could line the pump body with a layer of epoxy to build it up a bit.The seals seem fine , no leaking water,or air. The part that bends the impellor blades seems to be the actual pump body and that seems to be worn a little  The cover plate looks easy enough to make from stainless and I would say a local workshop could make 4 up fairly cheaply and have a couple of spares. { 2 motors both pumps look the same although only one is giving trouble so far]  $ 600 is for a similiar pump Yanmar price is $1400. Will have a look at Amazon, tried Alibaba but no success there.

[Steve Pope 243]

Some pumps do have a replaceable wear plate on the inner face. If it is a Jonson pump you will find that the piece that compresses the impellor is a replaceable part. It would be to diificult and expensive to machine the final shape. There should be a small screw directly above said compression point that holds the part in place.

[ex TL systems 63]

that would be good as it is a johnson pump , will have a close look when I am there next although from memory it seemed to be all one piece.

[wheels 543]

it is essential that the cover plate is not warn. If air can get past, the pump will not prime. If the pump runs too long with no water, the impeller will be damaged. I don't know how long plastic would work before it grabbed and melted or damaged the impeller, but good idea for a temporary fix. Don't use SST as you have too dissimilar metals screwed together and Saltwater. The SST shaft is isolated from the bronze by the seal, so you don't get a problem with that.
By the way, if you can grab the part Number off the old plate, that helps them greatly with getting a new plate. Many older pumps have discontinued, but other pump plates can cross reference with the number. That is what I found with my pump and the guy at the counter said write down the number for future reference.

[marinheiro 352]

useful article on pump rebuild

http://www.oceannavigator.com/March-April-2012/Engine-seawater-pump-rebuild/

I understand that the pumps Johnson supply to Yanmar are a unique OEM design for Yanmar, ie there is no Johnson equivalent, no doubt to protect Yanmar parts sales.

[wheels 543]

 

I understand that the pumps Johnson supply to Yanmar are a unique OEM design for Yanmar, ie there is no Johnson equivalent, no doubt to protect Yanmar parts sales.

I guess some may use that advantage, but it is usually because of the need to fit or drive the pump in a unique way to suit the design. Many engines, not just Yanmar, have pumps specific to the Engine. For instance, the pump may be mounted into the engine and driven by internal gears that are driving the Cam shaft of the engine.

[Marshy 30]

What about one of these?

http://www.speedseal.com/speedseal.html

[ex TL systems 63]

would be great if just renewing or refacing the end/cover plate would fix it but I would think that since I have reversed it and it still doesn,t prime indicates that the problem is also too much clearance in other places around the impellor. I mentioned SSteel to the guy that sells parts in Albany and he said that the new coverplates  he sells are SS , maybe they are isolated by the rubber o ring from the brass body.  The pump I have does not seem to have a replaceable wear plate on the otherside of the impellor to the cover plate, but maybe if one could be fitted there plus removing the wear from the coverplate may do it, otherwise will just need to get a new pump complete and keep the old one as a back up.Did consider removing the o ring and replacing with gasket sealant as that may move the plate a few fractions closer to the impellor and take out the gaps. Will try and find the place in Silverdale that can reface the plate or perhaps there is someone here in New Plymouth that can do that.

[Steve Pope 243]

To be able to re-use the plate get some emery paper / sand paper, put the paper on a flat surface and rub the plate using even pressure, you will soon have a flat (although slightly thinner) re-usable plate. Mind the end of fingers though.

[ex TL systems 63]

yes mine looks pretty much like the photo and no blockages in the pipes , once it gets going it seems to pump plenty of water, think I will bring it home and have a play with it , it is a pretty simple thing and I think it is just priming it that is causing problems, so will try a few of your suggestions. Another few hundred hours would be a few years use for me.

[Steve Pope 243]

look at your heat exchangers what could appear to be a poor pump may well be blocked tubes. On the photo above you will see the line where the squeeze plate (for want of a better word) meets the body of the pump, and the screw hole for the screw that holds it in place.

[ex TL systems 63]

blowing through/ into the outlet pipe seems pretty free but it would be worth having a look in the heat exchanger to see if it is clean , yes it would seem that a slightly bigger impellor would be better if that is an option, the motors have done around 1500 hours. I think they were new in 2005, not sure how long you would expect the pumps to last, guess if they were sucking up silty water they could wear a lot faster.   Outboard motor pumps seem to work fairly well/ even with worn impellors but the difference being that they are below water so do not have to pump air to get started

[rossd 16]

I replaced mine with a new Jabsco with same impeller size but different mounting which proved more of a problem than I first thought. In the end got a Johnson kit from Auss with new shaft and seal (cannot remember if it had a new end plate or not) and put the old one back on. If I ever have the motor in the workshop will make up proper mounting for the jabsco and put it on. At least they are current models and a bit more reasonable for parts.

[wheels 543]

Well that's interesting about the SST plate and the Bronze pump body together. 
 

Back to the pump of issue, Lets all just take a step back from possible issues with the pump. Don't go worrying about anything else till that cover plate is replaced first. Eliminate the obvious and most common. Keep the original impeller type. Don't go trying to fit in anything bigger. Which is unlikely you will find one anyway. The correct spacing or tightness of impeller is essential, as the lubrication is done with water of course, with water being the natural lubricant for rubber. Too tight and the rubber squeegees the water out and the rubber will heat up. I have seen a too tight impeller heat a cover plate hot enough to turn the plate a different colour and melt the rubber...... and burn my fingers when I couldn't work out what was happening and put my hand on it.
Providing the opposing wall of the pump is not too worn (and it usually isn't) , the rest of the pump can wear significantly without affecting the pumps ability to pump.
 

Hr's on a pump is a really hard one. Although 1500 is nothing anyway. My engine is approaching 3000 now and Pump is ok, just a new cover plate. And the wear the plate had may have been due to another separate issue anyway of running dry a couple of times in the past.

Oh and those speedy fit plates, great Idea, but haven;t been able to find anyone stocking them. I had often thought about making one myself, but trying to buy Bronze plate is too hard and expensive in NZ.

[ex TL systems 63]

I will be happy if that fixed it but.... when it suddenly stopped working at sea the first thing we thought was a blockage, then when that was ruled out an air leak in the suction side, then the wear in the cover plate, but I thought that turning the plate over , plus temporarily facing it with the plastic to take out any effect of the numbers stamped on the plate would be as good as a new plate as far as testing the theory. And you can see that it is fairly close to the impellor as the plastic shows some signs of wear after a few hours running.  When we put the intake hose in a bucket of water and ran the pump there was no water picked up , and no suction felt if you put your thumb over the hose, although once filled with water it will run fine.