Soak the corn in salt water for several hours to get the shucks moist. (Add 2 Tbs. salt to 1 gallon of water).
In a medium bowl combine mayonnaise, butter, sugar, lime juice, chili, garlic and pepper until the ingredients are well mixed.
Grill the corn, with the shucks intact, over hot coals or high gas burners on the grill, turning frequently, until done, about 30 minutes. The shucks will often turn dark/black but will protect the corn.
Peel the shucks back, one at a time, until most of the corn is exposed and then remove the silk. With a pastry brush lavishly coat the corn with the spiced mayonnaise-butter mixture.