Just an FYI for anyone thinking of replacing their Sherwood water pump with the Oberdorfer n202m-15 on an Universal M-35.
The replacement went pretty smooth for the most part. I encountered a couple of hickups during the replacement. No big deal, but I thought learning about them might save some time for someone who has the job planned in the not too distant future.
1. I had to order a 90 degree nipple because the water inlet and outlet hoses are located closer together on the Oberdorfer causing the 90 degree nipples to run into each other when you try to thread them on. To solve this problem I ordered a single 90 degree nipple from Catalina Direct that has a shorter barb for the hose, thus creating the clearence necessary to screw it on. Unfortunately, the new 90 degree nipple is meant for a different hose size than the original, so I elected to use my dremel tool to quickly grind down the barb on one of the original Sherwood fittings until there was enough clearance to thread it onto the Oberdorfer. Once I had the right clearence, I simply smoothed out the rough edges and voila, worked like a charm...and I didn't have to buy new hoses!
2. The Sherwood only requires two bolts to attach it to the engine block. The Oberdorfer takes four bolts. I thought about only using the two bolts to attach it, but then I thought "how stupid would that be when bolts are so cheap!" There are indeed four threaded bolt holes in the engine that perfectly match the bolt pattern on the Oberdorfer. However, the two unused bolt holes had allen screws in place of bolts to keep them sealed up. So I backed them out and bought 4 new bolts and lock washers. I didn't reuse the old bolts because they are too long and bottom out before they get a chance to tighten down on the Oberdorfer, so I bought the next size shorter. The new bolts are stainless steel...I hope that's not a problem in terms of dissimilar metals (anybody know anything about that?). And finally, as many others have talked about, I had to slightly grind down the top left side of the Oberdorfer mounting bracket so it would clear a post the sticks out of the M-35 just above it.
3. I finished off by pouring water in the Oberdorfer water pump and the hoses to prime it before attachment. This prevents the impeller from burning up when you first start it. I would have not have thought to do that if it were not for this website!
Anyway, hope this helps someone who might be thinking about doing the job in the near future. It was quite easy...even when you add in the grinding and the extra trip to the hardware store for new bolts/lockwashers.
1993 Catalina 36 Hull #1259
Newport Beach, California