Oberdorfer pump failing?

7 posts / 0 new
Last post
Gfreiman
Offline
Joined: 7/8/20
Posts: 6
Oberdorfer pump failing?

Has anybody ever known of an oberdorfer pump wearing out?  I have a 1983 M25 with an orberdorfer pump.  The water pump was working ok, but when I change the impeller it doesn't pump.  I put two new impellers in and neither one works.  The old one is too worn to run for another season so I need to address the issue.  I sanded the cover smooth and have run test by poring water down the inlet hose watching what comes out of the end of a discharge hose taken off of the heat exchanger.  I have seen some water movement doing this, but nothing like what i would expect.  I'm thinking that the inside of the casting could be worn out and preventing the impeller from working properly.  

Haro's picture
Haro
Offline
Joined: 11/7/14
Posts: 350

I wonder if it needs to be primed. Disconnect the incoming hose and pour some dishwashing soap in the pump and reconnect the hose. Check If the throuhull valve is open for the sea water and not blocked. 

pkeyser's picture
pkeyser
Offline
Joined: 5/18/13
Posts: 567

I would think that if the face plate can wear, so can the body of the pump, quite possibly to the point where it would loose suction. I suspect that the pump is original to your engine. My suggestion would be to replace the pump.

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

pkeyser's picture
pkeyser
Offline
Joined: 5/18/13
Posts: 567

Two other thoughts. Your pump probably has a paper/cork gasket on the face plate. If that gasket is too thick, it will reduce the pump's suction. Additionally, there are some low cost, brand knock-off impellers on the market. I've heard of dimensional and early failure issues. Are your replacement impellers from Oberdorfer?

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

Gfreiman
Offline
Joined: 7/8/20
Posts: 6

I have two new impellers that do not work in the pump.  The first came from Catalina Direct and the other is a Universal part.  I'm thinking I am going to need a new pump, brass should always win over rubber in a wear situation, but over 40 years and 309 or so impellers the inner lobes of the pump body must have worn down.
 

Catboat Willy's picture
Catboat Willy
Offline
Joined: 12/22/14
Posts: 384

Glenn; That's quite possible although it seems unlikely. Small fragments of sea shells, sand and other harder materials and get by the raw water strainer and get passed through the pump wearing out the impeller blades and possibly the lobes. I think I'd try some of the suggestions above before spending all that money on a new pump body. Keep us posted on how you make out.

Bill Dolan 1990 Catalina C-36 MKI - Hull #1041  'Williwaw'
Std. Rig, Walk Through, Wing Keel
M35, Oberdorfer Conversion,
Home Waters; Charlotte  Harbor & The Gulf Islands of Florida
'You are never out of work if you own a boat'

 

Gfreiman
Offline
Joined: 7/8/20
Posts: 6

I ended up replacing the pump with a new one and there is now substantially more water pumping then before.  The pump for a M25 is rated at 11 gpm so it should move a lot of water if everything is working right.  I have not tried the new impeller that would not work in the old pump, but I will do so next spring and post the results here.  So, it seems that the oberdorfer pumps do wear out over time.  Rubber will generally wear faster than bronze but over many decades of use and many impellers the bronze also wears.  My boat was built in 1983 (hull 55) and I am still using the original engine and I don't believe the raw water pump was ever replaced.

Log in or register to post comments