Well, it is one thing talking about seals being pressed into housing in the factory. New perfect surfaces, no need for sealer between the metal seal casing and housing. None of us are working with new engines. Keep in mind that the aluminum housings oftentimes get marred/scratched/grooved while attempting to remove those seals out of those housings. So, I always put a very fine film of OMC gasket sealer on the outer diameter of the metal seal housing during assembly. And yes, most of this get pushed up and kind of just rests on top of the outer diameter of the seal, so you sure want to apply it sparingly.
I am constantly frustrated when folks seem to believe that resealing one of these gearcases is simple/straight forward. Have you ever tried to get those seals out? Use some honkin seal puller/pry bar set up, and you will quickly destroy/gouge the delicate aluminum housing. These seals usually have a pretty tight interference fit into the housings as well.
The shift rod oring/seal offers its own challenges, pretty tough to remove/install it without the special tool. And, if you do coerce the oring out of the cavity without removing the bushing, chances are slim you will get the new oring back inside there fitting properly.
And lastly, there is the debate about the lovely gearcase/skeg “spaghetti seal”. Generally speaking, the spaghetti seal should not require any sealer, except around the ends where it butts up against the prop shaft bushing/seal housing. I use a thin layer of the dreaded type M/847 mainly underneath the spaghetti seal because it dries quickly and is super strong. This spaghetti seal tends to want to pop out of the machined grooves, especially during skeg installation. So, I rely on the type M/847 as a glue mostly, to make sure that darn spaghetti seal stays in place. The ends of the spaghetti seal must be properly trimmed as well. Another design flaw on these gearcases is that the skeg retaining screws are “inside” the spaghetti seal and pretty much rely on tight interference fit between the screw head and the skeg in order for these areas to seal properly. So, if the aluminum surfaces underneath the screws are damaged/not flat/gouged, another water leak will be introduced. I’m guessing OMC wanted to save money on specialized/precise fitting spaghetti seal that surrounded the retaining screws. And once again, parts assembled at the factory are brand new, imperfections/damaged surfaces are unlikely. I suppose a less expensive solution would have been to use retaining screws with grooves for oring…..Kind of like the pivot pin screws used on later models.
It amazes me how many people assemble these things and don’t do a pressure test. Keep in mind, there is a zero tolerance for any leaks. These things are not like car engines, there is no “dipstick” to check oil level/condition. And, keep in mind, that oil doesn’t just leak out, it is usually replaced by water inside the gearcase… If a car engine drips a bit of oil, no biggy, just keep an eye on it, and top it off every once in awhile, not really possible on one of these gearcases. I would agree that most could probably get one of these units back together and shifting OK, but sealed up properly?? Highly doubt it. In most cases, the amateur was probably better off with the milky gearcase he started with than the gearcase full of water he finds after resealing.
Now, consider the upset when you have carefully done everything to the best of your ability, and find a leak during the pressure test. Now, most likely the gearcase have to come apart again, meaning new spaghetti seal/oring. Imagine the thrill of having to clean all those mating surfaces up again, especially trying to clean the sealer out of the groove in the skeg.
