Sunday, February 25, 2018

Rebuilding the Raw Water Pump

Rebuilding the old Oberdorfer Water Pump

This is the Oberdorfer Pump that we removed and replaced with a brand new pump. At the same time that we purchased the new pump, we also purchased a rebuild kit for the old one (this) 

It's an M202M 15 Pump fitted to our M25-
XP Universal Diesel Engine on Eximius.

Not that old, but it was a rebuild that was on the boat when we purchased it, I suspect that the seals were incorrectly installed as both the Oil seal and the water seal both leaked.

Step 1 was to remove the old impeller, seals and inspect the shaft & bearing.

The corrosion around the O-ring shows how it was not very well prepared.

The indent in the cover plate shows where it wore.

The body of the pump shows it had leaked for a while, my fault for not fixing this issue earlier. 

I called Depco on the West Coast of Florida, and they were able to ship a new pump, and a rebuild kit within a few days of the order. Of course, that was nearly $400

I'll take better care to inspect and maintain the new pump.

The seal failure is clearly shown in this pic.

Both seals were leaking. The good news is that the leaks were evident from the Weep hole in the side of the pump.

I used the tool I made following the design by Ron Hill on the C34 Forum to extract the seals. 

It worked like a charm and I had both seals out within 10 minutes of getting to work.

Getting the Carbon shaft bearing out took a bit more brute force! I used a long socket that just fit and hammered to get the bearing out. Luckily, I was able to do so without damaging the pump body. 

This is the tool I made to press the carbon bearing into the pump body (the bearing is the black cylinder on the bolt) 

I put the Bolt, Bearing and nuts/washers into the freezer for 30 minutes while I came up with the rest of the plan.

I had already buffed up the pump body with an assortment of wire brushes, it looks like new. I'm comparing that to the new pump that we purchased.

The nut had to be outside of the pump body while pressing the bearing. 

Here's I'm using a 1" PVC Pipe connector as a spacer and a couple of 5/8" fender washers.

With the pump body clamped to my bench, I used the two adjustable wrenches to press the bearing.

The bearing has a chamfer on one end which I figured was the end that had to be pressed in first.

It went surprisingly easy, I could not turn the nuts by hand, but the two wrenches made it very easy. The technique was very effective and the bearing was pressed in within just a couple of minutes of it coming out of the freezer.

With the bearing installed, next was pressing in the two seals.

There's great info on the C34 forum site about how to do this. Basically it is done using a suitable Woodworking clamp secured to the bench and a sized socket as the pressing surface.

The Oil seal is inserted first with the side with writing visible while pushing the seal in place. I used a hammer to tap the seal in place. 

The Water seal is inserted second, the side with the writing on the inside this time. Again, a socket tapped with the hammer easily pushed the seal in place. I checked the insertion progress several time as it's important to have the seal fully inserted but not so far as to obstruct the weep hole.

Now if the Oil seal leaks, oil will come out of the weep hole, if the water seal leaks, then water will leak out the weep hole.

With the seals in place, it only needs the shaft and impeller installing.

The shaft was a snug fit into the seals and the bearing and did not have any play in it at all. 

The impeller was tough to get onto the shaft, I figured that the end of the shaft was damaged as the impeller would not fit over the shaft. I had to do some careful filing to smooth over the edge of the shaft. Once done, the impeller fit nicely. Not sure I'll be able to get it off again without removing the shaft, but that should not be a problem.

With the impeller installed, next the cover plate and O-ring and the grease screw.

Before inserting the grease screw, I applied a few pumps of grease from my grease gun and then rotated the shaft several time. The sound of the impeller blades flipping as they rotated around the pump body was very satisfying.

Last thing: Mark the cover plate with the date of the rebuild.

Next it will get wrapped in cling film and stored on the boat with the other engine spares.

Time to update the Service History.

See you on the water.


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