James Russell, who gained a reputation as an aggressive lender in tough times, resigned yesterday as president and chief executive officer of Mount Vernon Savings and Loan Association of Alexandria. He will be succeeded by John Simpson, a certified public accountant.

Mt. Vernon's chairman and major stockholder, Donald M. Eversoll, cited a "difference of style. Jim is a young man with very specific ideas. I feel he wants his own company." Mt. Vernon has only four stockholders.

During Russell's two-year tenure, Mt. Vernon's assets grew from $15 million to $117 million, as reported last June by the Federal Home Loan Bank Board. Russell, who was formerly with Perpetual Federal Savings and Loan, pushed sales of high-interest-rate "jumbo" certificates until they amounted to 82 percent of Mt. Vernon's funds. Mt. Vernon also acquired a savings and loan in the Tidewater area.

In this period, Mt. Vernon was one of a handful of S&Ls in the Washington area that operated in the black. For the six months ending last June, it reported a profit of $587,000. However, since that time, Eversoll said the S&L has had an overall loss, although he expects it to turn profitable again this month.

He admitted there were some deficiencies in its loan portfolio, but said most of the loans are current.