I want to write about men out doing whaling and fishing with the type of technology similar to that of early 1700s boating. They are going to have a blunderbuss, use old harpoon fishing, sail boats made of wood etc. However, I don't know as much about this subject as I would like to. Where could I learn more about how the men on the boat worked, what they did, how they whaled, etc?
There was an American author, Herman Melville, who, sometime around the middle of the 19th century, wrote a thousand pages book about whaling. While this is 1850 instead of 1750, the characters live and work aboard a ship, the Pequod, which is described as "a ship of the old school", "long seasoned and weather-stained in the typhoons and calms of all four oceans". Since it is unlikely that the readers will know the difference, if there is any difference, between the whalers of 1750 and those of 1800, I believe that Moby-Dick would do very well indeed.
An artists impression of the boats and whalers described in Moby-Dick. (Pictures from Wikimedia, public domain.)
For those readers who don't have a personal acquaintance with Moby-Dick: Melville likes to engage in long and loving descriptions of technology, processes, and culture. One can safely use Moby-Dick as a guide on how to hunt sperm whales. One can safely use White Jacket as a guide to the life aboard an early 19th century warship. While Moby-Dick is notorious for dedicating a whole chapter to the description of the harpoon line, White Jacket has an equally entertaining description of mast and spar technology.
But wait there’s more
There is an entire site, The Plough Boy Anthology, dedicated to 19th century American whaling; I would recommend Thomas Beale’s Natural History of the Sperm Whale, London, 1839. Containing: Its anatomy and physiology – Food – Spermaceti – Ambergris – Rise and progress of the fishery –Chase and capture – "Cutting in" and "trying out" – Description of the ships, boats, men, and instruments used in the attack; with an account of its favourite places of resort.
Boats attacking whales, from the Natural History of the Sperm Whale by Thomas Beale, 1839, available at the Plough Boy Anthology.
The Wikipedia article on the subject of sailing ships battle tactics is quite elaborate and detailed - definitely check it out : https://en.wikipedia.org/wiki/Sailing_ship_tactics
Do note this concerns mostly battle tactics. For specific tasks such as whalinh you might want to check out other articles.
Wind and water haven't changed
This means that you can hop on a modern sail-boat, and learn some things about 17th century sailing. Even on a dingy you can learn the difference between tacking upwind and running downwind. After a couple weeks you'll learn to see the pattern of wind upon the water and be able to predict when a gust will come.
If you're even more dedicated, it turns out there are even 'tours' for sailing tall-ships: http://www.maybe-sailing.com/
Why do this as opposed to just reading? There's a big difference between reading about the amount of force on a ships sail and realising that even a square meter or two of cloth can exert more force than any human can hold....
But some things have changed
Things like navigation, and the sail-rigs of the ships. For finding what these differences are, I'd suggest reading books, both fiction (As AlexP suggests) and non-fiction. If you live in a country settled via ships (Eg America, Australia, New Zealand) you can probably go to your local library and find first-hand accounts of the voyage written by the settlers who spent at least a month or two onboard those ships. Many of these diaries aren't publicly available online, so tracking those down will probably require some legwork.
Finally, here's a video from sailing a square-rigged ship: https://www.youtube.com/watch?v=96cRjLkIKlE