Gasket Sealiing Compound and 847 are entirely different products. 847 dries very quickly and sticky glue-like. Gasket compound dries only slightly and slowly and stays soft. Words chosen from my limited vocabulary.
I like your dictionary.. The 847 dries quickly, is tough to use, and is much stronger than the gasket sealer. The best use for the 847 is when gluing the spaghetti seal in place on the skeg. The spaghetti seal would just pop right back out of the grooves if you tried to use the gasket sealer. This is a very critical step indeed. Once glued in place, the spaghetti seal must be properly trimmed so it butts up against the prop shaft bushing and seals properly. Frank has posted pictures of this procedure in previous posts. The gasket sealer can be used under the skeg screw heads, on the upper bushing gasket, and the shift linkage pivot screw gasket.
OK, so you have compressed the lower driveshaft, did you measure it? You are correct, there is no easy way to peak inside at that shock spring, and there is no way to take the driveshaft apart. Measure the lower driveshaft length and post your results. You could “dry fit” the lower driveshaft and upper bushing housing together prior to actual assembly, then check for some end lower driveshaft end play. If there is no end play, or the lower driveshaft binds when “dry fitted” together, it is still too long and probably needs to be replaced….
To “dry fit” these items:
Install the lower driveshaft into the upper gear housing. Then install the upper bushing, SS plate, and impeller housing, then snug up the three water pump screws. You don’t need to install the gasket for this test. Then install the key and pinion gear while the upper gear housing is inverted. Spin the pinion gear buy hand, it should spin freely, no binding on the upper housing. Now remove the pinion and key, then flip the gear housing right side up quickly, you should be able to hear a slight clunk as the lower driveshaft drops down slightly, indicated there is some end play…