You cant use muff's on this engine. Remove the intake plate above the cavitation plate. Cut out a duplicate of this plate from sheet metal. Solder on a garden hose connector, and you have a better connector than muff's, or running in a barrel, for that matter.
Yes this is one of those with the small thin screen behind the prop. I thought that was the only intake point. Am I wrong? Is there another intake above the cavatation plate?
The intake behind the prop is the main one. The one above the plate is a secondary one for when running in reverse and water is being sucked away from the main one. It's just a couple of holes in a long rectangular plate.