jim81276.
How much increase do you want.
Lacking a lot of detail such as pump type, model, manufacturer., speed the pump is running now, product pumped and flow and head, a pump curve would held as would the impeller diameter if not full diameter.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)