How long does it take to get from Maine to Hawaii by boat?

It would depend on the boat, and on the route. In the 1800s, a sailing ship from Maine to Hawaii would involve going around Cape Horn at the southern tip of South America, and could easily take anywhere from 6 months to a year, depending on the weather.

A modern power vessel could get from Maine to Panama within 10 days, plus a day through the Panama Canal, plus 4 days to Hawaii. Again, depending on the weather.