I currently have 2 boats with larger motors, one being a Yamaha 115 and the other is a Johnson 150 that my dad had bought before he passed away. In my experience, the Yamaha gives me far less issues than the Johnson.
Buy a 4 stroke. Best extra money you will spend. Yamaha would be my choice.
One thing I will say for certain, whether you get a 4 or 2 stroke engine is be aware of the ethanol crap they have in gasoline now. Try to find a non-ethanol fuel source if you can, if not, use a good fuel stabilizer and run the engine often. The majority of issues I have had with not only boat motors, but small engines in general is the ethanol causing carb problems.
Congrats on the new motor. Time to see pictures of fish!