I saw some pictures of his issue. His stern tube hose has signs of cracking along the edge of the hose clamps, so to replace that hose, the coupling flange really does need to come off.
The socket and 4 longer bolts trick is good as long as you don't have to put so much force that the flanges will distort. I saw a puller on youtube once which had something that looked like a 3/8" round plate with 4 holes in it, a socket (or similar) at the center of it which worked with two bars that each had two bolt hole (slots) and a half circle in the middle for the shaft to pass through. This allows the force to be applied to the aft end of the coupler instead of the flange. Unfortunately, I can't seem to find this video now.
