The Council, on recommendation of the City Manager, may at any time by resolution transfer any unencumbered balance of an appropriation from one project to another under the jurisdiction of the same organization unit. During the last quarter of the fiscal year the Council, on recommendation of the City Manager, may by resolution transfer any unencumbered balance of an appropriation from a project under one organization unit to one under the jurisdiction of another organization unit. Transfers shall not be made from appropriations for debt service or other fixed budget items. The Council may at any time amend or revise the appropriation ordinance provided the ordinance as amended does not authorize the expenditure of more revenue than is estimated will be available.