Water Pump Question......

[BGadds]

Hello All, quick question concerning water pump designs.  I need to replace the pump on my '89 K75, cracked housing, long story.
Have a pump off of a '95 K1100 available.  Comparing the two, i see there are internal differences, most notably the size of the oil side gears and the impeller on the water side.  Cover is slightly different as well.  The newer pump appears to bolt right up to my K75.

Million dollar question, are they interchangeable?

Also, while I'm here, what is everyone's favorite sealant.  My manual specs out a product that can't be found....even on the net.

Thanks in advance for your thought.....

[frankenduck]

The water pump was redesigned and superceded the old one in 1990.  Yes, they are interchangeable.  Sometimes there's an issue with the cover not fitting (can't remember the details since it was a while ago) so check that too.

[BGadds]

thanks for the response.  the cover seems to be shaped differently up around the timing cover.  my old one was perfect so i used it.  Just finished a quick test ride, and all seems fine.  Main concern was the different sized oil pump gears causing a difference in oil pressure.

Since the weather seems to be holding today close to 70, time for a ride and look for leaks.

Thanks again.....this is my first BMW....a garage find that hasn't run in years.  Been a fun project.  So far it has been a joy to work on.  All the electrical gremlins have been tracked down and hopefully all the small oil leaks fixed.

Next, onto the brakes.

[frankenduck]

the cover seems to be shaped differently up around the timing cover.  my old one was perfect so i used it.

Could you post up some pics of the two WP covers and what the difference is, please?