I bought a used riding mower with a 17.5hp intek (B&S) model 37G777. Runs great, no smoke initially. Changed the oil and filter. Ran it foe several minutes, no problems. Went to mow the grass today and it started puffing smoke (oil smell), but it does not appear to be coming from the exhaust. Looks like it's coming from around the overhead valve cover. I put 48 ozs. Of oil per manual. Could that be too much? HELP.

Probably the valve cover gasket leaking.
Check the oil with the dip stick screwed all the way in.
48 oz sounds about right.
Luck

Maybe silly but... could you have spilled some oil into parts that get hot ?

Hope you fix it

Here's some additional information that might help. When the engine is cold it does not puff any smoke. After it is warmed up, it puffs smoke when the throttle is moved from idle to full throttle. A large puff of white smoke comes from the front of the engine (around the valve cover), but does not appear to be coming from the exhaust. But, I might be wrong about that. Based on my knowledge of small engines, if it were the valves or the rings, the engine would not run smoothly and would not have power, but this engine runs smooth and strong at all speeds and temperatures. This week I am going to change the valve cover gasket and check the valve stems for wear. Any additional advice will be greatly appreciated.