Oberdorfer pump

I have an Oberdorfer model 403m. I just replaced some parts and lowered my temps by about 7 degrees or better. I got most of the parts from Cardinal pump in St Louis. I got the end plate from Downwind Marine in San Diego.

If anyone is having trouble chasing down parts for these pumps both of these guys were good to work with. The cam and end plate were in pretty bad shape. The impeller was good but I went ahead and replaced anyway.

Keep the impeller for a spare?
I am pretty bad about checking or replacing impellers.
With me they are like out of site, out of mind until they leak or something overheats.

sdowney717 said:

Keep the impeller for a spare?
I am pretty bad about checking or replacing impellers.
With me they are like out of site, out of mind until they leak or something overheats.

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Keep a new one for a spare. Why would put a used one you chose to replace back in, only to replace it with another new one shortly? Impellers are to cheap not to keep a new one as a spare.

Ted

O C Diver said:

Keep a new one for a spare. Why would put a used one you chose to replace back in, only to replace it with another new one shortly? Impellers are to cheap not to keep a new one as a spare.

Ted

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Right now I have new ones for spares, but If I had an old one that appeared good no cracking vanes, I would keep it for a spare. From what I understand, even new ones can decay unused, the rubber can dry out. I dont often replace impellers, I know some people do them every year. On my engines, the impellers any bits will get stuck in the end of the HE, which in my case has one center bolt, so its very easy to take off that plate and look for a missing piece of vane.

All my impeller failures have been cracked off rubber vanes which then cause motor to overheat, I have not noticed any where they sit and take a set causing a cooling issue.

I had one where every vane stripped off the center hub, and prior to that everything was perfect. We had stopped and anchored, and when I started up in a minute it was overheating. I think it may have sucked in a jelly fish! So absolutely zero water flow was coming in and the impeller devastatingly fried itself.

sdowney717 said:

Right now I have new ones for spares, but If I had an old one that appeared good no cracking vanes, I would keep it for a spare. From what I understand, even new ones can decay unused, the rubber can dry out. I dont often replace impellers, I know some people do them every year. On my engines, the impellers any bits will get stuck in the end of the HE, which in my case has one center bolt, so its very easy to take off that plate and look for a missing piece of vane.
.

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Following your logic, if it didn't look bad, why would you replace it?

Ted

O C Diver said:

Following your logic, if it didn't look bad, why would you replace it?

Ted

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I would not. But that is me. I only look into the pumps if there is a noticeable problem. I had to fix a pump on a cruise just the one time due to failed impeller. The other pump fails were due to leaky seals, the kind Jabsco uses. I inadvertantly have found cracked vanes when fixing pump seal leaks.

Other fails have been due to worn end plates or the rubber impeller sides wear down and can no longer suck water.

I found out, (for me) some kind of corrosion buildup inside the brass jabsco face seal would jam the carbon ring from properly bearing on the ceramic washer.
I replaced several and then wondered what the heck. I took an old seal and soaked it in white vinegar and it freed up the ring, then they worked again.
I took one apart and found there is a tiny rubber o ring that seals the brass seal housing to the carbon face seal, and the brass was corroding and preventing the carbon ring from floating outwards to seal against the white ceramic ring.

The vinegar dissolved the internal corrosion and let it move again. If you have one of those seals in your hands, you should be able to press on the carbon face and it will go down and spring back up.

Sounds like you have a maintenance intensive raw water pump.

Ted

O C Diver said:

Sounds like you have a maintenance intensive raw water pump.

Ted

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It can be. But I did learn a lot about how it worked.
I would complain to other people about how leaky the Jabsco seals were for me and no one said they had any trouble with theirs, you know how that goes, everything is fine until its not.

I had a 403M on my old Hatteras and it was virtually maintenance free with extremely heavy use year around (we lived aboard). Here on the east coast Depco Pump in Clearwater is the go-to place for all parts, advice and if need be rebuilding; what a great company.

As simple way to insure that an impeller failure will be a minor event is to install a Y strainer between the impeller pump and the engine .


Some can be inspected for debris in seconds , if only the impeller could be changed as fast!

I just realized that I was mistaken. I did not have a 403M, I was thinking of our 104M HVAC pump. Never mind ! (other than the shout out for Depco). The OP picture should have clued me on that, duh.

There is usually a replaceable inner end plate as well. You can turn the plates over for 2x life.