Submerged when running! Only when you are going slow, up at speed is when they get a work out. They are simple to rebuild not saying they actually need it, that is your coin to flip! You mention Teflon tape, don't forget rule #1 always leave 1-1/2 threads exposed to avoid any bits and pieces getting into the assembly. Carl more than likely you already know that, but some are not aware the aggravation a tiny shard can cause.
Phil
No matter what your beliefs are "GOD BLESS AMERICA"
Fully retired marine tech near 60 years in the biz.