I have had no problem with it. I installed it over 200 hours ago. Only recently I noticed wetness near the weephole. I replaced the seals for about $50.00. I have several posts on this topic. To locate them enter my name in the search window.

My only “warning” is if the studs are loose coat the threads that go into the block with permitex #2. 
I replaced my -7 with a O-ring version of the -15.  

Very happy no greasing the pump every 10hrs and can check impeller without requiring a new gasket.  Also no worries about adapter falling in engine or getting miss-timed    

Les

Wally;
 I think you'll gain quite a bit by reading previous posts regarding the Oberdorfer water pump. Mine is at 700 hours and still going strong.  If I were you, I would buy the kit that contains the new smaller hose elbows, (you'll need these as you old sherwood elbows are too large) plus new hold down flanges and new new high tensle strength screws - rather than just the pump assembly. You'll find several models that can & will nicely replace the exsisting Sherwood pump.I'm using the two stud model (no grinding nescessary) and it perfectly fits my M-35.
You might want to talk with Cardinal Pump in St. Louis, MO at https://www.cardinalpump.com/  (314) 628-0100. Tell them you are with the Catalina 36 forum and they'll throw in free shipping (or at least they used to).
Last picture shows the part number for the kit I referenced above.

I installed the Oberdorf last season, M35 AC, because of the easy access to the impeller.  No problems so far, purchased spare impeller and gasket but haven's install them.