In Core Results web part, you might have noticed that even though you have checked "Show More Results Link", you are not able to see the "View more results >>" link on the screen even if the results are more than the number mentioned in "ResultsPerPage" property.
After spending some time and investigating this issue and with the help of google search, I found that there is one more web part property which needs to be updated. Without this, View More link will not be visible.
The property name is "MoreLinkUrl". But this property is not visible from UI.
So how to update this property?
Edit the Page and in edit mode, export the core results web part. Open the exported web part in notepad. You will find "MoreLinkUrl" property like the following.
Edit the property to add the link of newly created page in Pages library. This new page "MoreResults.aspx" will host a core results web part of the same configuration and will show ALL results as per the search scope.
After editing the .webpart file, upload it to the Web parts gallery and add that web part to the main page.
You will now see the "View More >>" link on the main page and it will have redirection link "MoreResults.aspx".