Impeller doesn't fit

[Pete G]

I set about to replace my impeller.  The one on the shaft took a lot of coercion to remove, and the replacement does not fit.  I went to my mechanic and he gave it a shot with an arbor press, and it destroyed the impeller.  Looking on Catalina Direct, I see a late and an early Oberdorfer.  Any suggestions?


https://www.catalinadirect.com/shop-by-boat/catalina-38/engine/engine-cooling/water-pump-impeller-kit-late-oberdorfer/?SearchResults=1

https://www.catalinadirect.com/shop-by-boat/catalina-38/engine/engine-cooling/water-pump-impeller-kitearly-oberdorfer/?SearchResults=1

Does anyone know if there's a difference between the two, and if so, what it is?  My engine is #500056. 

[scgunner]

Pete,

I've got an early boat too #273 and I've been using the one with the paper gasket for years, I don't think there's any difference between the impellers. You can check the inside of the cover to see if it has a "O" ring.

[Pete G]

Here was the answer, but my "lathe" was a file on the outer lip.  The mushrooming wasn't visible to me, but hey, I have bad eyesight.

Your axle end seems mushroomed, was that before or after trying to fit the new impeller? Seems you hammered on it. Get it cleaned on a lathe, and check the diameter of both axle and impeller. I've seen people use freezer for the axle to have tiny bit of lower diameter, but it might be also the wrong shaft / wrong impeller combination.

[Ron Hill]

Pete : I agree that all Oberdoffer (models) impellers are the same diameter and width!! 

Just use some dishwashing soap and compress the blades to slide it in place!!

A thought

[Jon W]

Pete, on the Catalina Direct page scroll down to Technical Support. "Two Versions of the Oberdorfer Pump" will answer your questions.

[Ron Hill]

Pete : I reread your initial post and I had the same problem. Right after I got my C34 that summer we were out for a sail and coming back in I turned on the engine. 1st Mate was at the wheel when she asked me to come up as the exhaust sounded "funny". We were overheating!! The temp gage read over 200F!! I shut down the engine and told her "No sweat" as I had a new impeller and would go back below and change it out!!

I took off the Oberdoffer face plate pulled the impeller attached to the shaft out. To my surprise I couldn't (like you) get the impeller (3 blades missing - hence the overheating) off the shaft.  So we sailed to the dock. She asked if we were going to practice our docking? I told her NO practice as it was like a wheels up landing - no practice.  We docked OK!!

I took that impeller and shaft home put it in a vice and hammered the impeller off the shaft!! Even had to get a bigger hammer!! Why the impeller was fuse to the shaft (bronze/brass impeller to a stainless shaft) is unknown!!! 

So you aren't the only one that has had this problem. From then on I always put some grease on the inside of the impeller before I put it on the shaft!!

A "war story",but always use some grease or Chapstick when you have 2 different metals.  A few thoughts 

[KWKloeber]

Pete

Where did you get the impeller that did not fit? 
I presume that you removed the cir-clip?

1. There is no difference in impellers for the two kits that CD sells.  The difference is the paper cover gasket (for the older "202M series" pumps) vs. the rubber cover o-ring (for the current "N202M series" pumps.)

2.  I  have posted about a zillion times to dab SuperLube gel on the shaft of the pump and hub of the impeller to help prevent corrosion between the two.

If they become stuck, take a box end wrench that the shaft just passes through and hang that end over a sturdy step or wall (not hang it off the DOCK!) and step on the other end.  Use a bolt or pin smaller than the shaft diameter to tap the shaft out of the impeller hub.  Alternately, you can use a piece of pipe that the shaft just slips into to hold the impeller hub.