myculturedpalate.com/shrimp-boil/

1-2 cups seafood seasoning (such as Old Bay®), or to taste
NOTE: Old Bay for a richly seasoned East Coast boil. Choose Zatarain's Crawfish, Shrimp, and Crab Boil for a spicier, Louisiana-style boil
18 pounds new potatoes- at least one per person
6 lemons, quartered
2 sweet or yellow onions, peeled, quartered
4 bay leaves
6 tablespoons kosher salt
4 tablespoons whole black peppercorns

24 ears fresh corn, halved, husks and silks removed

SEAFOOD and MEAT
16 pounds whole crab, broken into pieces
14 pounds fresh shrimp, heads off
OR 25-30 pounds shrimp
9 (16 ounce) packages cooked kielbasa sausage, cut into 1-2 inch pieces

3 12 quart pots. Fill each stockpot with 6 qt. water (if using 5-6 6 quart pots, divide ingredients and water among them). Divide and add lemons, bay leaves, salt, peppercorns, and seasoning, cover, and bring to a rolling boil. This takes about a half hour.

In the following instructions, start timing each section when the pots return to a FULL, rolling boil.
Add potatoes, return to a boil, and cook 7 minutes, up to 10 if potatoes are larger or large chunks. Add onions, return to a boil, and cook 5 minutes. Add corn and sausage, return to a boil, and cook until corn is cooked and potatoes are tender when pierced with a knife, about 5-8 minutes more.
If crab is included, add with the corn and sausage.
Finally, add shrimp and cook (no need to return to a boil), stirring gently, until shrimp turn pink, about 3 minutes. Remove insert or drain through a very large colander.