"If you are going to buy a 4 s
"If you are going to buy a 4 stroke, get a Honda - great reputation, solid motors etc etc.
Personally though, unless you need a 4 stroke due to regulations (restricted lakes etc) I would go with a 2 stroke.
In a 2 stroke, for overall quality you can look for a Yamaha - they built pretty much every small 2 stroke out there over the years (except for OMC's) and produce an outstanding motor...
They require way less maintenance, are generally lighter and cost a few bucks less to buy and hundreds less in upkeep over the years - plus they stand up considerably better to neglect or complacency.
Whichever you choose, do not buy a single cylinder motor, you will not be pleased with it, they idle like crap and always seem jittery no matter how well they are tuned.
Ultimately, if you do choose a 4 stroke, make sure that you are willing to follow the service schedule to a "t" or you will quickly turn you nice new motor into junk. You can't treat a 4 stroke the way old 2 strokes are treated - run a few weekends a year, same plugs for 5 years straight - no service etc - if you do you will be buying another nice new motor in 2 or 3 years...."