Up north, Social Security is a weighty public policy issue, debated impressively in the abstract. But here in this sun-drenched retirement town where more than a third of the population is past 65, the issue is grittier, and the generational combat hand to hand.

Merrie Zucker, 20, a teller at Atlantic Federal Savings and Loan, is a worker paying the Social Security tax. "I can't believe how much . . . Social Security takes . . . every week," she said. "I don't make that much, I'm trying to make a start in life and the retired people just take their chunk of my check.

"I'm not going to see 1 cent of that money when I get old. There won't be any Social Security . . . . I'm just giving this money away."

The elderly take a different view.

"For 40 years I was paying Social Security," said Gene Alpert, 63, of Boca Raton, who is retired. "I didn't complain. No greed. And I had no opportunity to sock away money in IRAs [Individual Retirement Accounts] and Keoghs [tax-deferred retirement funds for the self-employed] like young people today . . . .

"When we paid Social Security, a dollar meant more in relative value, in terms of our earning capacity, than the money being earned today. So don't tell me we didn't put in enough. We put in our share. They can put in their share now."

These are the poles in the issue that politicians probably fear more than any other this year: whether, as part of the deficit-reduction plan now building in Congress, to freeze Social Security benefits by delaying the cost-of-living adjustment (COLA) that otherwise would take effect Jan. 1, 1986.

President Reagan, often burned by the Social Security issue in the past, has said he will approve such a freeze only if a bipartisan majority in Congress goes first.

Senate Majority Leader Robert J. Dole (R-Kan.) has said that Senate Republicans, who are taking the lead in budget deliberations, have tentatively agreed to support such a freeze.

Social Security makes up about a fifth of the budget, and the argument is that senior citizens should do their share to retire the deficit. A 12-month deferral of the COLA would save about $6 billion in fiscal 1986 and $22.1 billion over three years.

Part of the issue is equity. The budget-cutters already are going after COLAs in other benefit programs. "If we do nothing on Social Security , then why should we treat the next group differently," Dole said in an interview.

But Social Security is sensitive because of its reach and its nature.

Benefits go to one-seventh of the population. For 65 percent of the elderly, Social Security is the largest source of income. As benefits have risen, the percentage of elderly people below the federal poverty line has declined.

By the same token, almost all wage-earners pay the tax. And many, especially the working poor and middle-income two-earner families, pay more in Social Security taxes than in federal income taxes.

The tax burden may intensify as the baby-boom generation moves into retirement and the ratio of workers to Social Security recipients declines. The burden also has been exacerbated in recent years because of high inflation. In several years Social Security benefits have increased faster than the wages that are taxed to pay them.

Thus, the politics of the COLA are sharply etched.

"It's a matter of intergenerational transfer," said John Makin, director of fiscal studies of the American Enterprise Institute. "We're still in the stage where the benefits Social Security beneficiaries are receiving is far more than the money they paid into the system. Current workers are subsidizing them . . . . Now we're asking this generation of retirees to contribute something to the younger generation" by forgoing next year's increase.

The politicians joust uneasily on the issue.

Rep. Claude Pepper (D-Fla.) recalls that at a recent breakfast budget briefing for members of Congress, Office of Management and Budget Director David A. Stockman was asked how likely it is that the administration might make further cuts in its defense buildup. Stockman replied that defense cuts might be possible if Pepper, a senior member of the House Select Committee on Aging, would help freeze the Social Security COLA.

"I said, 'Mr. Stockman, we are just supporting our president,' " Pepper, 84, said he replied, throwing an elbow at the budget director by recalling Reagan's campaign pledge not to cut Social Security benefits.

"I'm personally going to make sure the president is able to stand by his solemn pledge he made during the campaign to our nation's elderly," Pepper said.

In this seaside community, where rafts of middle-class retirees have come south to live in modest condominiums set among the affluent retirement estates and country clubs in Boca Raton and Palm Beach, the young are quite aware of who is paying for the Social Security checks that flood the banks here during the first week of every month.

Talk show host Al Rantel of WNWS radio two weeks ago asked listeners: "Should social programs be cut to balance the federal budget?"

The rules for answering were hostile to the elderly: No one over 55 could participate because "they couldn't be objective with Social Security putting dollars in their pockets."

The response from the younger set was nearly 75 percent in favor of cutting social programs. "Most of them volunteered that Social Security has got to be cut," Rantel said. "My show gets a lot of people in their thirties and forties. And they said they're putting money out for old people, and they'll never get a dime back. One guy put it real well. He said the old people are ripping us off . . . . They are mad, furious at these old people."

In Century Village, a large complex of three-story condominium apartments around a lake, a 69-year-old who heard the broadcast and who is a member of Senior Pac, a Washington-based lobbying group for the elderly, smiled when asked about the resentment of workers whose paychecks are taxed to support Social Security.

"I went on a panel at college, and the kids kept saying they don't like Social Security," said the retiree, who asked not to be identified. "They said why should they support the people who are sitting on the beach retired. They see us living down here, and they think somebody's rich. Well, I told them. I said, 'You know what would happen if you didn't pay Social Security? Mom and Pop would come back home, they'd be asking you to send them a check!'

"You could see those college kids suck in the air," he said. "One girl said, 'Oh, God.' "

The 4.1 percent Social Security COLA in the president's budget would boost the average Social Security benefit for retirees $228 to $5,532, according to the Social Security Administration.

For the middle-class retirees here, that would be a small dent in their budgets. But a quarter of Social Security beneficiaries rely on Social Security for 90 percent of their income. Fifty-five percent of Social Security beneficiaries have incomes below $10,000; 73 percent below $15,000 and 90 percent below $25,000.

The prospect of losing an average of $228 because of a one-year Social Security COLA freeze prompts the elderly here to condemn the younger generation's "greed."

"They are chipping away at the system," said Florence Goldmann, 73, acting head of the Senior Pac chapter here. "We've had a six-month COLA freeze in 1983 when they said we had to do it to save the [Social Security] system. Now they say they want a one-year freeze. This year there is a tax on Social Security if your income is above $25,000 for a single person and $32,000 for a couple .

"They are chipping away at it, and pretty soon it won't be an entitlement program," Goldmann said. "It will be welfare. They want to say, 'If you are not poor you don't need it, darling.' Hell, no. Why is it, when it comes to older people, they all want to know how poor you are? I don't know why old people have to be poor."

According to the results of a study by the American Association of Retired Persons, a one-year COLA freeze in 1986 would increase the poverty rate for persons 62 and older from 13.5 percent to 15 percent, pushing 553,342 people into poverty.

Laurie A. Fiori, a Social Security analyst for the AARP, notes that the one-year freeze would affect future Social Security payments by lowering the base for future COLAs. In the five-year period, 1986 to 1990, she estimated, the one-year freeze would cost an individual $1,284 and a couple $2,160.

The Congressional Budget Office estimates that a one-year freeze would save the government $7.4 billion in fiscal 1986 and $27.2 billion for the 1986-88 period.

Here in the 14th Congressional District of Florida, where 43 percent of the population is over 65, Rep. Daniel A. Mica (D-Fla.) finds himself walking a political tightrope between young and old.

"It's a difficult situation," Mica said in an interview. "When I look at Social Security I have to understand the rebellion of the young against higher taxes and I have to understand the needs of the elderly . . . .

"My district is well-to-do, Boca Raton, Palm Beach. But when I have office hours in the district I see elderly people who bring me their checkbooks to show me how tough it is for them to make it. One man told me he tries to eat fresh meat once a week . . . . If that happens in my district, then you can understand the impact a one-year freeze on COLAs will have on the elderly."

On the other hand, the young are increasingly dismayed about Social Security, according to polls, as their doubts harden into conviction that, despite their contributions, they will not receive Social Security benefits when they retire.

Even the rescue plan meant higher payments for the younger generation, with the Social Security tax rate slated to rise from 7 percent today to 7.51 percent by 1988.

"If I could quit paying Social Security taxes right now in exchange for not taking a dime out of Social Security, you better believe I'd do it," said Jim Jaspers, a Boca Raton hotel clerk. "I need the money."

According to a January Washington Post/ABC News poll, Americans are evenly divided on whether Social Security will exist when they reach retirement age. According to the poll, 47 percent say they think it will exist and 47 percent say it won't.

Of people ages 18 to 30, two-thirds doubt that the system will be there when they need it. And in the 31-to-44 age group, 55 percent say they think Social Security will be defunct before they retire.

Even among people nearing retirement, persons aged 45 to 60, nearly a third say they think Social Security will be a memory as they try to pay for retirement.

But for those receiving Social Security payments, such as David Friedman, a retired Teamster union organizer, the debate over the COLA freeze is but an echo of his daily budgeting: the money for medicine for him and his wife, such as the Zylopin for his gout that costs $10 a bottle; the increasing utility rates and the way "prices at the Winn-Dixie [supermarket] keep on climbing."

"I've got Social Security, I've got the interest on my savings and that's about it," he said. "I'm all right. I don't have to ask my kids for anything. I like it that way. I think they like it that way. But you start playing with Social Security, and I may need something -- it changes the relationships."