Raw Water Pump Gasket

Kevin Henderson · February 18, 2013, 09:40:31 AM

I have been diligent about changing out my impeller every year on my Oberdorfur raw water pump. My old impellers have always looked pretty good and I keep them tucked away for an emergency spare if needed. One thing that I always get when purchasing a new impeller is the paper gasket that is also replaced each time.
I recently purchased a roll of some gasket material. I took a new existing gasket and outlined a template. I then took an exacto knife and cut out a new gasket forom this material. The gasket material I bought is somewhat thicker than the original paper gasket material. Is this a safe thing to do? Will this type of gasket (Home Made) work if I use it or should I forget this DIY approach.
Has any body else done such a thing?

Ken Juul · February 18, 2013, 10:02:58 AM

I'm not familiar enough with the Oberdorfer design. I do it all the time for the paper gasket on my Sherwood. If the thicker gasket increases the volume of the pump cavity, you may cause problems.

Stu Jackson · February 18, 2013, 10:14:38 AM

Quote from: Kevin Henderson on February 18, 2013, 09:40:31 AM
this a safe thing to do? Will this type of gasket (Home Made) work if I use it or should I forget this DIY approach.
Has any body else done such a thing?

Kevin, it's safe to do it ONLY if you use the same thickness material. What I have done is to find paper bags that are the same thickness as the OEM gasket paper. For example, shopping bags simply WILL NOT do, 'cuz they're too darn thick, so small bags, like for tiny stuff at WM or a hardware store, works just fine. Too thick and the pump won't prime or work.

Ron Hill · February 18, 2013, 03:18:51 PM

Kevin : As the others have said - your gasket needs to be "paper thin". If it is not then the impeller blades (on the sides) are not sealed with the walls of the pump and you are not pumping the best because of poor suction. A thicker paper gasket moves the face plate further out breaking that impeller side seal.

You don't really need gasket material, thin paper will do nicely. A thought

Jim Hardesty · February 18, 2013, 04:22:04 PM

Kevin,
Good that you are saving the lightly used impellers. I'll pass along what I've been told about storing impellers. I was told to coat them with vegetable oil and keep them in a zip lock bag. New or used. When I change them I use my new spare then put the just bought one as a spare, to be used at next change.
Jim

Ron Hill · February 18, 2013, 05:01:14 PM

From my limited experience of about 30 years with gaskets and impellers, I have always coated them with silicone to keep them nimble.

I'd guess that an organic oil like vegetable oil could get mildue, mold and break down!?!

A thought

Stu Jackson · February 18, 2013, 05:05:38 PM

After all these years (too

), I've found that you can buy "kits" that include impellers, gaskets and seals. The cost of gaskets is sooo low...

Terry Forshier · February 20, 2013, 09:09:23 AM

I canged the impeller on my Orbendorfer pump last week. I had ordered a globe impeller (the blue one) awhile ago and was going to put that on. However, the two fabric type washers that press into both sides of the impeller on the shaft would not fit into the recessed holes on the side of the globe impeller. They were too big. So I had an original impeller and used that one.
Incidently, I thought that the impeller was faulty because I was not gettimg much water out the exhaust. This did not fix things. I then checked the intake and the filter and they were good and flowing. then I took off the hose leading from the heat exchanger out. The exit hole was plugged. A screwdriver popped the material free when recommected the water freely came out the exhaust. Looked like salt and or calcium buildup. Whatever it crumbled and flowed out the exhaust.

Ron Hill · February 20, 2013, 02:53:35 PM

Terry : As I recall the Globe impeller for an Oberdoffer is a #815. All the Globe impellers I've seen have a brass insert in the middle. That insert fits on to the stainless shaft that turn the impeller.

I don't recall any "looseness"(slop) in the fit on to the shaft.

Stu Jackson · February 20, 2013, 08:14:33 PM

Beware of Globe impellers.

http://c34.org/bbs/index.php/topic,5298.0.html

TonyP · February 20, 2013, 10:10:22 PM

Down here in Oz, ours is a Johnson pump (never a mention of them from you northerners), maybe modified, as others not available but works fine with part of a sailing magazine page as a gasket I made when I had some trouble with no raw water one night with the engine running. I had a spare impeller but no gasket.

enjoying our summer sailing

cheers
Tony

Ron Hill · February 22, 2013, 02:59:09 PM

Guys : It appears that the blue (Globe) and the black impellers fall in to same category as "the best anchor type", "standard vrs synthetic oil" and etc etc sailing/boater products !!

I have no idea on Stu's personal experience with the Globe impellers and I also have no idea on Mainsails' photos on how long they were in the pump, number of hours run and how often those impellers were periodically inspected??

I can only give you my personal experience :
Over the past 26 seasons I've used the black (in the beginning) and then blue impellers. I have never lost a blade off of the blue one, but have plucked out a number of black blades out of the exhaust elbow of an Oberdoffer.
Now let me mention that I take the my raw water pump apart in the fall of every season and thoroughly inspect the impeller and spray it with silicone. When that impeller is reinstalled on the shaft, it is turned around so the blades will be bent in the opposite direction during the next season. In my spare water pump I NEVER store the impeller inside the pump housing. Don't want the blades all scrunched - up. My extra impellers are sprayed with silicone and stored in a Zip-lock.

On my new engine with a Sherwood pump I have never used a black impeller, only the blue Globe impellers and haven't had a problem in the past 3 years with the same impeller.

My thoughts

Terry Forshier · February 22, 2013, 05:58:33 PM

on the original impeller *(BLACK) there is a little fabric type washer that seats into each side. The globe impeller (BLUE) has a recessed place on each side but the washers did not fit into them. (they were just a bit too small). there was no slippage and they fit well on the shaft. Are the gl;obe impellers ok to use without this? Also there is no gasket on the newer orbendorfer pump.there is a rubbber ring seal on the face. I hope this clears this up.

Ron Hill · February 23, 2013, 04:32:49 PM

Terry : I stopped using the washers on the sides of the Oberdoffer impellers back in 1990 and had no problem.

Yes, the new Oberdoffer pumps have an "O" ring rather than paper gasket - just like the Sherwood 908 pumps have had for years.

A few thoughts

Stu Jackson · February 23, 2013, 06:55:50 PM

Quote from: Ron Hill on February 23, 2013, 04:32:49 PM

Yes, the new Oberdoffer pumps have an "O" ring rather than paper gasket - just like the Sherwood 908 pumps have had for years.

The difference between the old and new Oberdorfer pumps is model #

Old: 202M-15

New: N202M-15

Interestingly enough, N seems to be for "NEW"

The difference is the gaskets.

DEPCO is THE source, as Ron always has advised us.