I used to specialize in Porsche repair with a sub-speciality in 914's. Even after I specialized in a single
model of car there was a huge variation in the time it took to do the same job on a different car. Replacing tie rods, for instance. On a very clean car with few miles I might be able to replace them in 40 minutes. On one car they were rusted on and I had to remove most of the front suspension for access, cut them off and weld big nuts on the stubs and it took me 6 1/2 hours. The book said to charge 2.1 hours.
I can't imagine the **** you'd run into in a boatyard with all of the hundreds of boat models, in a marine environment
, with the most widely varied maintenance
and repair history
Every boat job is a custom job, from my perspective.