Actually just bought my boat and its not in the water yet--waiting to have the bottom painted. A friend in Milwaukee also has a Colgate 26 and has a 5hp 4 stroke Nissan (around 60#''s). It is about 10#''s heavier than the Yamaha, and he says it works great. Remember, the boat was designed to have an instructor in the stern, and that could add a couple hundred pounds. I usually won''t have anyone back there unless my wife lets the 5 & 8 year olds go back there (fat chance).
The Yamaha 4 stroke I''m told is whisper quiet and doesn''t vibrate, and has FNR. It has an small internal tank (I think about 2 liters). The engine is much more efficient than a 2 cycle, so it wont need to be filled often. Also you can plug in an external tank if you want--don''t think I''ll need it.
Cost was $1030. I couldn''t find a lighter 4 or 5 hp 4 stroke outboard than the Yamaha, and they have an excellent reputation. Also, I''m keeping the boat at a slip, so I need the FNR.