This is a tuff and ugly subject but here is my 2 cents and I am not a fisherman - strictly googan
Everyone tips differently and have there own views of services rendered.
Personally on a party boat with the daily pool I generally give 20%-50% - really not a problem with me since I dont win them often
The other day I was on a half day boat and won the pool - it was really , really hot and fishing was real slow - I didnt think the mates were going to get tipped well so I gave them 60%. That is just me. (They worked there azzez off BTW for everyone)
These guys work hard and I feel they deserve it . Some dont
Standard is 18%-30% like any other service you receive - the better the service the bigger the tip.
Some people dont believe in tipping some do - is what it is - right , wrong or in-different - too each his own and I can only worry about what I do and how I treat other people - IMHO
Gdubs-
