Or let's put it this way.
A professional needs to keep a timesheet, to know how much to bill the client, and to attempt to make a living.
An unskilled amateur will spend a long time learning skills and techniques, and doing everything slowly and carefully, with much time spent in figuring out how to do things. To keep a timesheet would be meaningless, but certainly the unskilled amateur is going to take much longer.
A skilled amateur will decide on the level of complexity, finish and accuracy that is to be aimed at, and this will vary widely between builders, so again a timesheet would be meaningless.
There are a few meaningful statements one can make, though, such as:
" Building a boat takes at least twice as long, and costs at least twice as much as the number you first thought of".
The best advice I can give to a first time builder is to Keep It Simple! That's the best way to get a project finished and to get it finished at a reasonable cost and in a reasonable time.