The nation's 24.1 million elderly persons have political influence out of proporation to their numbers because so many of them vote, the Census Bureau said yesterday.

The fact that 62 percent of those 65 years old or older voted in the 1976 election, compared with 49 percent of those aged 18 to 34, was one of the most striking features of a statistical snapshot of the elderly the Census Bureau released.

It means that in a struggle between the old and young over the use of public and tax monies to support retirement and social services, the elderly would have an extra measure of political clout.

With their large numbers, heavy voter turnout and potential to become a single-interest bloc on issues of income and medical care for the aged, the elderly could constitute an increasingly formidable force in U.S. politics.

Of the 24.1 million Americans aged 65 and over in 1978, the Census report shows, 14.3 million are woman and 9.8 million men. Two-thirds lived in families, either with a mate or with children or other relatives, but 30 percent lived alone and 6 percent were institutionalized.

About a million lived in nursing homes, an institution that has expanded enormously in recent years with the availability of federal Medicaid money to pay for out-of-home care. About two-fifths of all Medicaid outlays go for nursing home costs.

Nearly 2.5 million of the persons 65 and over were working in 1978. Most were in service trades and retailing, but a handful were employed in mining, construction and other heavy industry. About a third of those working were women.

Median family income for the aged was $9,121, much of it from Social Security and pensions. The median income was substantially below the overall national figure of $16,009 for families of all ages.

About 3.2 million, or 14 percent, of the aged had incomes below the poverty line. The percentage for persons of all ages was 11.6 percent, indicating that poverty is more widespread among the elderly. However, the number of aged in poverty was much lower than in 1970, when 24.5 percent of those over the age of 65 showed incomes below the poverty line.

Seventy-two percent of elderly housemaids lived in homes owned by them.

Elderly persons suffered less form crime than the young: about 30 crimes per 1,000 population compared with 130 per 1,000 for younger persons, according to the Census Bureau.