Hi all. I know this is an old post, but I want to close the loop as it were. To recap, I wanted to use the far superior Oberdorfer N202-908 raw water pump in favor of the M35B's "standard" Sherwood G-908. The Oberdorfer is better made and easier to service than the Sherwood, and there have been stories of catastrophic failures of the Sherwood. Kind of a no-brainer. However, I noticed when I swapped out the Oberdorfer for the Sherwood I started to see steam in my exhaust, which I attributed to insufficient cooling of the raw water due to the Oberdorfer's lower pumping flow rate. I knew many people had swapped out the pumps on M25s so I thought it might be an artifact of the M35.
I had replaced all the hoses, both fresh and raw, and was using a newly boiled-out and refurbished HX, so the only explanation seemed to be the raw water pump. I settled into a routine where I'd use the Oberdorfer for day-to-day getting in and out of the slip day sailing, but if we were going to "go" anywhere (>25 nm say) I'd swap in the Sherwood. Boy am I good at swapping out raw water pumps.
So end of last summer after our 250nm circle to Catalina I prepared to take the HX in for cleaning and refurb. My one was installed in May 2009 by the PO, and it would be my third refurbishment. I thought "maybe it's time" and started looking at buying a new one. The Universal replacement (part 201027) is breathtaking ... over $800. However, the internets led me to a company called Go2Marine in Seattle that sells an American-made drop-in replacement for $396. Great quality of the HX, great support from the company.
And no steam in the exhaust with the Oberdorfer. As I mentioned, I did this all end of last year, but didn't want to post anything until I'd given the new HX a workout. We just finished our 250nm trip (with water temps up to 77deg F.) with the new HX and the Oberdorfer, and no issues.
So perhaps there's a limit to how often an HX can be boiled out and still be OK. I still think an inefficient HX and an Oberdorfer is a bad combination, but the problem is with the HX more than the pump.