paris
Well-Known Member
My 2gm has a Johnson raw water pump installed, the body is fairly worn and rather than wait until it fails I would like to either renew it or get it machined flat (if it can be done). Has anyone done this before?
Johnson water pump refurb?
- Thread starter paris
- Start date
Daydream believer
Well-Known Member
2 assumptions. First that it is a similar pump to the one on my Volvo MD 2020 if not read no further
Second assume that you want to do this to solve a loss in pump performance on intake side & you have some leaks.
Does the body need machining or is it actually the cover? The body may have the slightest indentations that can be solved by rubbing over a carpenters coarse stone. Reducing the housing depth may mean the impeller rubs on the cover.
The cover can be sorted by cleaning the paint off with stripper & reversing it so that an undamaged face is pointed inwards. However, sometimes the part no. is engraved rather deeply.
Alternatively buy a piece of 3mm Th brass on line & make a new one ( my solution) if the exorbitant cost of a new one annoys you. The hole centres are actually circular so if your cover is shaped ( like the volvo ones) it need not be. No reason why it cannot be a little oversize. Cutting it can be done with a hole saw with the centre drill removed & drilling through 2 pieces of ply clamped over the brass. A piece of brass to do 2 covers cost approx £4-50 from M- Machines online. It can also be cut with a coping saw & a couple of blades.
Another thing one can do is buy a tube of the blue gasket compound & apply it, but insert 3 pieces of smallest cable tie at 120 degrees between cover & housing until compound starts to go rubbery. Then gently remove the ties & complete the tightening down process. This fills any indents & is better than the useless paper gasket.
Second assume that you want to do this to solve a loss in pump performance on intake side & you have some leaks.
Does the body need machining or is it actually the cover? The body may have the slightest indentations that can be solved by rubbing over a carpenters coarse stone. Reducing the housing depth may mean the impeller rubs on the cover.
The cover can be sorted by cleaning the paint off with stripper & reversing it so that an undamaged face is pointed inwards. However, sometimes the part no. is engraved rather deeply.
Alternatively buy a piece of 3mm Th brass on line & make a new one ( my solution) if the exorbitant cost of a new one annoys you. The hole centres are actually circular so if your cover is shaped ( like the volvo ones) it need not be. No reason why it cannot be a little oversize. Cutting it can be done with a hole saw with the centre drill removed & drilling through 2 pieces of ply clamped over the brass. A piece of brass to do 2 covers cost approx £4-50 from M- Machines online. It can also be cut with a coping saw & a couple of blades.
Another thing one can do is buy a tube of the blue gasket compound & apply it, but insert 3 pieces of smallest cable tie at 120 degrees between cover & housing until compound starts to go rubbery. Then gently remove the ties & complete the tightening down process. This fills any indents & is better than the useless paper gasket.
paris
Well-Known Member
Thanks for the reply and a good tip about making a cover. The cover is worn a little but my main concern is the actual body of the pump, I hope I could get it machined flat again.
RichardS
N/A
If by "the body of the pump" you mean the front facing which the face-plate affixes to, then you could easily flatten that yourself with a piece of glass and a sheet of fine wet and dry or similar. It does not have to be a precision fit as it doesn't operate under high pressure/vacuum conditions and usually has a gasket/O-ring to aid sealing. I would be surprised if a new gasket/O-ring and plenty of silicone grease doesn't seal it but, if not, sanding the pump face and face-plate as described will be 100% effective. You can tell when the job is done by the gradual change in colour of the sanded face,
Richard
Charlie Boy
Well-Known Member
Pictures would help here. At the moment I can’t tell if the faceplate is worn or is it the inner face (on the other side of the impeller)? Johnson water pumps aren’t that expensive, certainly they cost a lot less than a heat-damaged engine does to repair or replace. In your shoes I would buy a new one, then look into refurbing the old one, just for shits-and-giggles really. Of course, a side effect is it means you have a spare.
paris
Well-Known Member
Yes the inner face is worn (other side of the impeller), the faceplate has wear but I can flatten that easily. I think I will end up replacing with a new one before it stops working altogether (it’s currently running ok). I just want to plan for the future and safeguard the engine and boat.
I will look for a source of a pump without the Yanmar tax added hopefully.
Charlie Boy
Well-Known Member
paris
Well-Known Member
Thanks Charlie, seen this one, the one from these for my engine is £260. Hopefully should be ok?
Moodysailor
Well-Known Member
Replace the pump. If you machine down either face (plate or body), or if they get worn too badly then the pump will lose pressure as the water will escape around the end of the impeller rather than being pumped through the engine. I don't think there is a service option for those small pumps.
For this reason, I also only advise using the paper gasket. Smear it with a thin film of grease between finger & thumb and they are fine., you don't need to use any sealant. Mostly the reason the paper gaskets leak is because there is a burr on the pump body where a screwdriver or similar has been used for impeller removal which keeps the end cover proud and stops the gasket from sealing. A light dress with a file will sort this.
I change my impeller every year, so the gasket gets replaced as part of the service, I've replaced thousands over the years as a marine engineer - never a problem.
Definitely change it before it is too late - these things will not give you much warning if it's going to fail, and they never fail at a convenient time.
It will be a generic Johnson pump, so if you can find the original Johnson numbers you can probably get a good deal online. Chances are it's used in a bunch of different applications.
For this reason, I also only advise using the paper gasket. Smear it with a thin film of grease between finger & thumb and they are fine., you don't need to use any sealant. Mostly the reason the paper gaskets leak is because there is a burr on the pump body where a screwdriver or similar has been used for impeller removal which keeps the end cover proud and stops the gasket from sealing. A light dress with a file will sort this.
I change my impeller every year, so the gasket gets replaced as part of the service, I've replaced thousands over the years as a marine engineer - never a problem.
Definitely change it before it is too late - these things will not give you much warning if it's going to fail, and they never fail at a convenient time.
It will be a generic Johnson pump, so if you can find the original Johnson numbers you can probably get a good deal online. Chances are it's used in a bunch of different applications.
TSB240
Well-Known Member
I have recently refurbished my replaced pump. I mounted the body in a lathe and took a minimal skim off the inner impeller seal face sufficient to remove the scores worn by the impeller.
A similar amount was taken off the gasket seal face of the body certainly no more!
The only problem with doing this is you can significantly reduce the threaded length in the body for the plate clamp screws.
If the wear is really bad you will strip these threads very easily when tightening the outer plate screws.
I have used milliput epoxy putty to build them up to give them more than original thread.
The compression wedge ramp needs to be removed prior to any machining of the inner face. Replace it before machining the sealing face.
Steve.
A similar amount was taken off the gasket seal face of the body certainly no more!
The only problem with doing this is you can significantly reduce the threaded length in the body for the plate clamp screws.
If the wear is really bad you will strip these threads very easily when tightening the outer plate screws.
I have used milliput epoxy putty to build them up to give them more than original thread.
The compression wedge ramp needs to be removed prior to any machining of the inner face. Replace it before machining the sealing face.
Steve.
Poignard
Well-Known Member
The Johnson pump in my BUKH engine has a wear plate that can easily be replaced. Does the OP's pump have this? If so he can easily replace it (or perhaps reverse it).