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Hey Fleetwin – Good summary of what most of us hobby guys have learned over the years by trial and error!
When you talk about water replacing gear oil and no dipstick, it made me think of my 1996 ski boat with a MerCruiser Inboard/outboard drive. It has a tube coming up from the top of the gearcase, to a plastic see-through reservoir with a filler cap high up in the engine compartment. In most cases, as gear oil leaks out, it gets replaced by more gear oil due to the static pressure from to the height of the reservoir above it, and I can see if there is a problem if I have to add often, and it’s an easy add, just pouring it in. This would be a great thing to have on outboards, especially bigger ones. It’s not perfect though. I had the gearcase driveshaft seals dislodge – there are two of them pressed in and both came loose, and were crooked. I was adding so much gear oil that I drained the gearcase to see what came out, and there was also a lot of water getting in, but the water stayed low, and emulsified into the marine gear oil as it should but couldn’t migrate up to the reservoir where I could see it. When I bought replacement seals, I learned there was a change (probably because a lot of them were dislodging) that added a plastic retainer between the two seals, taking up space so they couldn’t dislodge to a crooked, leaky position. Note the OEM seals had this change, but Sierra did not.
Dave