Looks like an early version of the Model R Fastwin. It changed dramatically in 1928 to become a Model H where horsepower jumped from 4 to 12. There was a huge difference in motors between 1927 and 1928 in all brands. The only reason I indicate it is a Fastwin is due to the size of the muffler. There were also 2 versions of that motor based on the gearcase and ‘you have the later version. The earlier version had a gearcase similar to the Model N with the reversible bottom end. For some goofy reason, Evinrude (and Ole wasn’t part of the team then) used undersized compression fittings on the waterlines. They are about .050 undersize. So if you go to the hardware store and buy some 3/8ths compression nuts, they will be real sloppy in fit.