Your YM147D has far less Hp than my V-twin Craftsman mower. To get it to till-the-soil and move you along would place great strain on the little machine. Even the King Kutter XB may be too much for your tractor. It's designed to be the smallest CAT-1/-0 tiller on the market right now.
http://www.northerntool.com/shop/tools/product_200311201_200311201
Now, with that said, there are 4-ft tillers that have drive motors to run the tiller independently. Most PTO tillers need around 30Hp to do the job properly.
Years back, Simplicity, Workhorse and other 3pt CAT-0 lawn tractors had these mini-tillers. Hunt around for those.
MF/Snapper Garden Cat-0 PTO tiller 42" 1855 is one of them. Some of the CAT-0 tiller are 2,000rpm and other 540rpm. Thus, when you find one, look up the specs on the web or email the seller to ask. There are RPM reducers too. Just got to know what to connect.
AND, your YM147D will need front weights too. Many of these tillers range from 400lbs to 600lbs.
Maybe it's time to upgrade to a larger Yanmar?