Are you looking for English ancestors in the time period before passenger lists were kept?
I have an index to Surnames of Emigrants from England to USA 1773 to 1776 now available at
Surnames A start at
There are a total of 1,814 names (Surnames A to G) online, with the rest following as quickly as I can transcribe them. When complete there will be over 6,000 names for you to search.
Remember that this is an INDEX to names along with page numbers for reference.
After finding an ancestor in the index, you will need to obtain the full record on microfilm or in published books. Instructions are given online as to how to do this.