Leakage may be oil that has passed thru motor and is dripping from exhaust
That is normal. If not the case more investigation needed.
50 to 1 may be a little thin especially for running flat out maybe not
for trolling at slow speed and oil is "TOP QUALITY." There are some
who have had adverse experience with some brands of oil in some motor
AND there are those who state a belief that this brand or that is the
cat's meow. Best opinion is even the most expensive oil used generously
is cheaper than parts destroyed by running too thin too hard.
The truth of the matter is this today's outboard oils and lubes are better
and some are better than others. Motors have changed too. It is an apples and oranges comparison to figure out how much of which modern oil to add to today's no lead gasahol. Probably somewhat less modern oil but not as thin as for
more modern motors. Some outboard makers thought they were making outboards
that could live on 100 to 1 ratios...and warranty claims soon changed their
thinking. I would suggest a TCW-3 with an outboard makers brand on label
mixed at motor maker's ratio and read the spark plugs. Your use and
motor's needs should agree.
It is important to mix accurately and consistently from batch to batch