Oil at rear of raw water pump, corrosion

[Geoff W.]

So I was going to replace my Oberdorfer pump on my M25 due to noticing some leakage of salt water underneath it. Upon removing it I find something fairly concerning - oil dripping from the back of the raw water pump, and perhaps worse block corrosion than anticipated.




so, what am I looking at? That bottom post came out as I was unscrewing it, and that whole corner looks like it’s missing a chunk or something. Are those posts standard parts somewhere I could buy, or universal specific? The one that came out had some stripped threads so I’d like to replace it.

and... oil where it shouldn’t be is scary. I haven’t found any evidence of water in oil but perhaps my smoke issues have been oil in water, albeit very slight. Any guidance appreciated.

 

[Christian Williams]

Mine just bolted on. Dunno what the posts are.

You know, to the casual observer, the channel of corrosion under the pump suggests that lower bolt was not holding, the calcium is from sea water, and maybe the gasket was missing or shot. Perhaps you could tap the hole and put it back on tight and see what happens. I don't see any real oil leakage, at least not running down the engine block.

Not trying to be a Pollyanna, others will know more.

 

[Geoff W.]

Mine just bolted on. Dunno what the posts are.

You know, to the casual observer, the channel of corrosion under the pump suggests that lower bolt was not holding, the calcium is from sea water, and maybe the gasket was missing or shot. Perhaps you could tap the hole and put it back on tight and see what happens. I don't see any real oil leakage, at least not running down the engine block.

Not trying to be a Pollyanna, others will know more.

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Maybe a very silly elementary question but is there supposed to be oil on the back side of the raw water pump at all?

 

[Frank Langer]

There is a water seal and an oil seal, both of which can need periodic replacement as part of normal maintenance.
Frank

 

[Guy Stevens]

The oil is normal and expected, there is oil in the block we definitely want it to be there!
The corrosion not so much. However it is covered by the pump flange, so if you clean it up well, and makes sure the aluminum block is electrically separated from the bronze pump, and that both the oil and sea water seals are good, you should be alright.
G

 

[Kenneth K]

Geoff,

I haven't replaced a RW pump yet, but I'm guessing it won't be long until I do. Like Guy said, this (from the M25 parts manual) shows the pump mounts to the gear case. The gear case would be full of, well, gears, and is the same housing that the oil filter mounts to. I'm guessing there is oil sloshing freely around in there to lubricate the gears.



Behind the gearcase? My guess would be that the upper gear and shaft (driven by the camshaft gear) in this picture is what drives the water pump.



As for the post that came out--the manual shows it as part 300096-STUD. If it's in good shape, I'd re-use it--just tighten two nuts against each other and use the nuts to screw it back into the gear case. Likely, the nut on the pump side of the stud rusted itself onto the stud, so the lubed part of the stud inside the block came out with less friction.



If the stud is damaged, I'd probably be paranoid enough to buy the replacement part from Westerbeke. If you buy one off the shelf, it could be a different steel hardness than what they used, and then would it hold torque differently than the other studs.

 

[debonAir]

There is a little disc oil flinger on crank shaft that throws oil all over inside that gear case so yeah, you want to see oil behind the pump. But you don't want to see oil ON the pump because there is supposed to be a gasket between the pump and gear case cover.

Those studs are normal equipment for the tractor your engine was made for. That spot is where the hour-meter is normally attached. On some of our engines, there is an adapter plate that sits on those 4 studs with recessed nuts, and the raw water pump bolts to that adapter plate, and there is a little shaft-extender piece that sits inside the adapter plate. As far as I know, the only reason for the adapter plate version is that they were building engines so fast at some point they couldn't source enough of the direct-mounted water pumps so adapted another pump footprint. I bet they never imagined that most of those engines would still be running these many decades later.

To me, it looks like your lower stud backed out a bit and let oil leak around the flange and sea-water drips from the pump seep in and corrode the gear case cover there. There is NO pressure in there, so a bunch of Silcone form-a-gasket and re-tourque the studs and nuts and it should be good to go unless the raw water pump is leaking. You don't want the pump leaking sea-water into the oil. If some got in there via the flange leak you should change your oil at least

For a new pump, partsandpumpsonline was super good to deal with (and 1/2 the cost) when I replaced mine. As mentioned, the pump's shaft seals are serviceable, but my pump's front was worn more than the seals so replaced the whole thing. Getting a water past the pump seal into the crank case is a pretty bad scenario and hard to see when its all closed.

 

[Geoff W.]

Thanks all. I'll hunt down a replacement stud as the one I pulled out was in pretty rough shape, and I'd rather have a nice new one in there. I have the standard replacement gasket coming in already but with the pitting, would something like Form-a-Gasket as mentioned by DebonAir be a better choice for the now irregular surface?

 

[debonAir]

why not both! I'd put a small bead of some silcone gasket maker under the paper gasket.

If you have a Kubota tractor dealer nearby they probably have that stud in stock if you dont want to wait.

 

[Geoff W.]

Hi all, long time no see. My previous installation of this seems to have failed as I now have a steady drip from the bottom left corner of my raw water pump. Maybe 1-2 drops a second. I'm currently cruising, I think the right fix is to go home and build it back up with Bondo, but any ideas on how I could plug the leak underway? Slather some form-a-gasket on it? I definitely do not like the saltwater all over my engine.

 

[Christian Williams]

Sounds like you need a new seal.

When this water leak happened to me offshore, I rigged a funnel under the drip, into a bottle, so I could keep track of the flow. I emptied the bottle every few days.

I don't think such a drip should cut a cruise short. You can later press out the seal, or do what I did--buy a new pump.

 

[Geoff W.]

Hello fine ladies and gentlemen -

Trying to tuck in the corners around this install. It was still dripping saltwater on the engine which was making the engine sad, and thereby making me sad.

Also, I seem to be running into an interesting bit of corrosion:


This is after I wire brushed it a bit. Is something not electrically separated here? I'll check my zincs but maybe the raw water zinc is dead? The studs were also showing pink de-zincification corrosion when I pulled them out. I've put them back in with tef-gel this time but ran into some issues with the new stud not being quite long enough to get a good purchase on the nut.

I might go with bolts like Christian showed above -- Christian, do you happen to know what size of bolts you've got in there?

 

[Christian Williams]

It was a while ago--something like 8mm cap screw. I tend to go to the WM racks and ... guess.

 

[Geoff W.]

It was a while ago--something like 8mm cap screw. I tend to go to the WM racks and ... guess.

Same here. Grab a few of the size down... a few of the size up... a couple lengths shorter a couple lengths longer...

 

[Prairie Schooner]

. . . and build it back up with Bondo, . . .

Hi Geoff,
It's kind of late for me to chime in, but here goes. I wouldn't use Bondo. It is a polyester resin product and would not be very heat resistant. There are epoxy products which are specifically heat resistant. Some can even be drilled and tapped, though I wouldn't count on them to hold major loads. I'm following this post with interest as I'll be rebuilding our Oberdorfer in the next month or so. Good luck!
Jeff

 

[Michael Edwards]

Prairie Schooner, I glad you caught that “Bondo Comment.
This is an easy fix fix for JB Weld. Put the stud in to mold around, degrease the area. Put a lump of JB on; slide the pump into position to press the surface of the gooo flat; wait ; finally, gasket and gasket sealer, and, it should be fine for a very long time.
Those pumps are simple to rebuild. Wear inside the pump from abrasion can be a deciding factor.

 

[G Kiba]

JB Weld works fine. I have found the products from this site interesting. Some of the engineers at my work use these products from time to time. I think I saw stainless steel spay paint as well! Very interesting stuff.

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[Pete the Cat]

Hi Geoff,
It's kind of late for me to chime in, but here goes. I wouldn't use Bondo. It is a polyester resin product and would not be very heat resistant. There are epoxy products which are specifically heat resistant. Some can even be drilled and tapped, though I wouldn't count on them to hold major loads. I'm following this post with interest as I'll be rebuilding our Oberdorfer in the next month or so. Good luck!
Jeff

The Oberdorfer web site has a very short video of how to rebuild the pump with the replacement bearings and seals. FWIW.

 

[Second Star]

Concerning getting water into the crankcase, there is a weep hole between the water seal and the oil seal. This allows any water that gets by the water seal to drain out so it isn't under pressure and likely to get into the crankcase past the oil seal.

 

[Pete the Cat]

I don't think there should be oil in the space I am seeing it in the picture. Did this oil drip from some external part of the engine or is the bearing seal to the engine block cam driving the pump leaking? As Christian suggested, I would probably just clean it up, put a good gasket and stud on it and put it together. But I would check it in a few hours to see if you have a leaking bearing seal to the cam driver for the pump--or maybe it is just coming out through the stud hole--but I do not think it should be there at all. Eventually, that could be a problem. Unless I am getting something wrong.