My Water Pump Impeller "Adventure"

[odaydokay]

This turned out to be a bit of a a struggle, when in fact it should be easy. When I bought this (Oberdorfer) pump from Depco, it came ready to mount with impeller installed so simple bolt on deal, replacing my old Sherwood which had failed after 30 years or so. Now that 5 years have passed (low boat usage each year, maybe 8-9 trips average) I decided to replace the impeller with one I got from Depco same time as the new pump, so a factory original type as far as I know.

So, the old one came out easily using a screwdriver to hold the shaft and needlenose pliers to pull the impeller out. Saw no broken or cracked vanes, but went ahead and installed the new one as intended. (Will keep the old one for an emergency.) Slid it onto the shaft, but “hey, what’s going on here…?” it would not go on all the way, maybe 1/8 to 3/16 left to go! Tapped it a bit, still no go. Finally, pulled the shaft out and tried to get it to go on by tapping. Still not on far enough to get the circlip on. Finally had to drive home so I could use my bench vise to tap the shaft downward and off the impeller. Greased the heck out of it, but it still stopped about 1/8” from the “stop point”. Took a block of wood as buffer and tapped with hammer and it finally went to the stop. All easy after that, but I am wondering what the heck that was all about.

I will say, in general, on these type pumps (not Sherwoods as then you must reinstall the whole pump) removing the entire shaft makes the job easier than working on it in place. But if you get an impeller like mine, you will have the same struggle I did. No amount of grease will help.

Hope you all get impellers that are friendlier than this one. There are a lot of worn machine tools in this country maybe this part came from one of them.

 

[Ralph Johnstone]

Took a block of wood as buffer and tapped with hammer and it finally went to the stop.

I'm wondering what will happen when you try to install a new impellor 5 years down the road. Hammering the impellor into place is the easy part (relatively). Pulling it out does not impart anywhere near as much force between the two mating surfaces. If possible, you should investigate the problem now and be prepared to go after the supplier if the impellor won't come off. If you've got a caliper around, take a few measurement if you can get the impellor off.

 

[Richard19068]

Interesting. Lots of people say you don't need the snap ring. I don't use it. But in your case i assume it was a clear indication that the impeller was not fully seated back on the shaft.
As with Raplh Johnstone, I would be a bit leery about having to tap it on with a hammer.

 

[Stu Jackson]

Why does anyone even consider forcing something when it should be a simple slip fit?

Just because it is a boat shouldn't mean that common sense should go out the window or portlight.

Would you try this on something in your garage? Wouldn't you ASK here first?

Ralph's right.

 

[Calif. Ted]

(Will keep the old one for an emergency.)

Toss it, I don't think you'd really want to re-use that old rubber impellor in a couple years. First, I'd take it along for comparison to buy a new impellor that didn't require a hammer to install.

 

[Terry Cox]

Our Genset came with an Oberdorfor sea water pump. Long story short, ours requires an OEM (Onan) impeller and OEM gasket. Anything else and the pump will not prime. Never had a need to hammer it on or to seat. Slides on nicely.

 

[odaydokay]

I see all of your viewpoints, but setting the impeller and the shaft in my vice without gripping it impeller flat on top, shaft pointing down required only a minor tap using a bolt somewhat smaller than the opening. Taking it off in a few years should not be any harder as I don’t imagine it’s gonna get tighter I know this is strange but the thing is pumping water just fine and I am satisfied with the result. I do think I will contact Depco about this, however. Thanks to you all for tuning in.

 

[odaydokay]

This in from Depco' tech. Makes me feel a tad better.......I guess.

I am not sure why the impeller didn’t want to go on easily. I can say all it takes for that to happen though is a burr on the shaft or a little mushrooming at the top of the shaft just above the little snap ring groove. In the past, I’ve had to take a file to the shaft to get an impeller to go on like it’s supposed to. Happy to hear the pump is working well for you. If you have any more issues, questions, or concerns, please feel free to reach out to me here in the service department.

 

[Ralph Johnstone]

Possibly, yes. BUT it doesn't mean you'll be able to get it off five years down the road. I'd suggest taking it apart now and correcting the problem rather than waiting until it's time to do it five years later when it's developed a light coating of corrosion and it's not coming off for love or money.

Your boat, your choice.

 

[StanleyJ]

This turned out to be a bit of a a struggle, when in fact it should be easy. When I bought this (Oberdorfer) pump from Depco, it came ready to mount with impeller installed so simple bolt on deal, replacing my old Sherwood which had failed after 30 years or so. Now that 5 years have passed (low boat usage each year, maybe 8-9 trips average) I decided to replace the impeller with one I got from Depco same time as the new pump, so a factory original type as far as I know.

So, the old one came out easily using a screwdriver to hold the shaft and needlenose pliers to pull the impeller out. Saw no broken or cracked vanes, but went ahead and installed the new one as intended. (Will keep the old one for an emergency.) Slid it onto the shaft, but “hey, what’s going on here…?” it would not go on all the way, maybe 1/8 to 3/16 left to go! Tapped it a bit, still no go. Finally, pulled the shaft out and tried to get it to go on by tapping. Still not on far enough to get the circlip on. Finally had to drive home so I could use my bench vise to tap the shaft downward and off the impeller. Greased the heck out of it, but it still stopped about 1/8” from the “stop point”. Took a block of wood as buffer and tapped with hammer and it finally went to the stop. All easy after that, but I am wondering what the heck that was all about.

I will say, in general, on these type pumps (not Sherwoods as then you must reinstall the whole pump) removing the entire shaft makes the job easier than working on it in place. But if you get an impeller like mine, you will have the same struggle I did. No amount of grease will help.

Hope you all get impellers that are friendlier than this one. There are a lot of worn machine tools in this country maybe this part came from one of them.

I'll tell you what I discovered with my Oberdorfer pump on a Universal M-12 engine. The rubber around the center bushing on the new impeller may have to be slightly trimmed (about 1/16") with a utility knife blade to get it to seat deep enough to install the circlip. I replaced my impeller this year and the rubber in the center of the impeller overlapped the bushing slightly. The removal allowed me to seat the impeller deep enough to install the clip. This does not affect the vanes or performance.