Need to replace a Briggs 17.5 engine

[Bigstone]

I have had troubles starting the 17.5 Briggs engine (2 of them) forever.  Probably due to the compression release and or the I can only fit one of the garden tractor batteries in the mower so it spins t slow.   I'm looking at a used Kohler magnum 20HP MS engine. Are these any good? How do they compare to the Kohler Command engine? This issue has bugged me too long.  Would either of these Kohlers be a suitable replacement? Or will I have the same issue. All of the connection on the mower have been cleaned.  Any help with this would be much appreciated.        

Dave