You don't need no stinkin' puller!
Go get yourself some longer bolts.... about 1 Ĺ " longer with threads all the way to the head
Remove the OEM flange bolts, and replace with the longer ones loosen the set screws and spray some penetrating oil
on the shaft side flange/shaft joint.
Pull the shaft back (out) about an inch. Take a nut (any nut that's outermost points are less than the diameter of your shaft), sandwich it between your output shaft and the prop shaft; tighten the bolts.... it "should" push the shaft out as you tighten (remember to tighten incrementally on opposing sides); repeat, adding more nuts as you go.
IF the shaft refuses to budge, its time for Rosebud (an acetylene torch). Heat the prop side coupler (try not to burn up your boat) while there is tension on all the bolts. In real difficult couplers, a helper may be required to "tap" on the extreme prop end of the shaft.
in 40 years, this has never failed me... that said, some have been VERY stubborn!