You’re on the right track here but would it be feasible to make and install a second liner, out of the same material you used for the first one? I’m thinking that would give the vanes firmer contact with the liner lessening the chances of them being bent away from the liner because of resistance to the water. Your brass liner will probably last longer than the aluminum alloy used in OMC pumps.
This photo is all I could find of an OMC impeller in its housing and the vanes have good contact all around. Even the one that’s bent backwards.
