I did not intend to ignite more rage over the Sherwood vs. Oberdorfer debate.
Someday I may opt to buy the Oberdorfer pump, but I still wince when I see how much smaller its pumping cavity is. Two years ago I posted some calculations to back up my concerns over its lower capacity for motors over 30 hp. But I realize that many people use it on their 35 hp M35B motors and are happy with it. I am not ready to try it now, but maybe someday.
The simple fact is that a third company has now come out with an all-bronze knockoff of the Sherwood at a fraction of the cost (around $400). That's worth discussing. Competition between different pump companies is good for the consumer.
I am not bothered by "backwards" direction of the Sherwood pump cavity. I'm able to get my skinny fingers behind it to remove the 3 screws, and to pull the cavity off the impeller without having to disconnect the hoses. However I am bothered by the potential for rust causing failure of the G908 bearings. So the opportunity to buy an all-bronze Sherwood knockoff for $400 is worth my consideration. But only if I can confirm that JMP is a reputable pump manufacturer, and that it matches the pumping volume of the Sherwood. That's the reason for my question about cross-compatibility of the impellers - that would answer my question about its capacity. I know that JMP recommends using their impeller -
every company recommends using their own replacement parts. But if JMP is selling their replacement impeller for use in the Sherwood G908, that suggests that the pump cavity is the same size.
So rather than beating the Sherwood vs. Oberdorfer horse to death, I'd love to hear comments from someone who has actually seen the JMP version.
EDIT: I just answered one of my questions. JMP sells their own replacement impeller (#7172-01) as a replacement for the Sherwood impeller (Westerbeke #200175).
https://www.jmpusamarine.com/products/7172-01k-jmp-marine-flexible-impeller-kit/Therefore, the pump cavities are the same size. Based on this, I might purchase the JMP and keep my Sherwood as a spare. I'll think it over some more, and look to see if there are happy customers out there somewhere.