JMP markets their impellers as replacements for the Sherwood impellers, so it stands to reason that if JMP were to someday disappear that you could pop in a genuine Sherwood impeller into the JMP pump.
Another option is to send your leaky Sherwood out to be rebuilt. Depco rebuilt mine several years ago for about $100. They only had to rebuild the water-side seal - a full rebuild would be more.
Interesting that you think your Ob pump has too little flow. I've always been concerned about the design being on the edge for warm water locations. Yours is the first time I've heard about a potential flow deficiency in a cold water location. FWIW, Depco and Hansen Marine both advised me not to use the Ob for engines above 30 HP. My M35B is 35 HP, so I won't install the Ob. Others feel differently, but many of them have the smaller engines.
Another option is to send your leaky Sherwood out to be rebuilt. Depco rebuilt mine several years ago for about $100. They only had to rebuild the water-side seal - a full rebuild would be more.
Interesting that you think your Ob pump has too little flow. I've always been concerned about the design being on the edge for warm water locations. Yours is the first time I've heard about a potential flow deficiency in a cold water location. FWIW, Depco and Hansen Marine both advised me not to use the Ob for engines above 30 HP. My M35B is 35 HP, so I won't install the Ob. Others feel differently, but many of them have the smaller engines.