I have made a habit of befriending my local boat mechanics. They like to be tipped and remembered a Xmas.
I always ask if I can watch or lend a hand and if they baulk, I just explain that I might need to effect a similar repair when I am far away from them.
Once you get "their nose open", it's amazing how many tips they will share. I think some repairmen like owners that take an interest in maintaining their own boats and it is in the repairman's self-interest to "show-how-to" the easy jobs, changing impellers, engine oil
, etc. because they know you will call them for the valve adjustment...