It is 6:00 a.m. Frank Wisneski arrives at his office on the 27th floor of the Bank of New England building in Boston, a stone's throw from the Old State House. Like a lot of businesspeople, he reads The Wall Street Journal, checks some printouts of the previous day's activities, and plans what he will do today. Unlike most, he will have a lot of other people's money riding on every decision he makes.

Many mutual funds these days are investment portfolios of a couple of hundred million dollars. A hundred million here, a hundred million there, as the late Sen. Everett Dirksen might have said, and pretty soon you are talking real money.

T he job of figuring out what to do with all that money belongs to the fund's portfolio manager. Sometimes the manager is a committee, as with the Kemper funds and a few other big groups. And sometimes he or she is more of an administrator than a decision-maker. The managers of Value Line funds, for instance, make their buyand-sell decisions largely with reference to the firm's well-known stock-picking system (see INC., September, page 168).

But more often than not, the responsibility for all that money falls on one individual -- on, as Frank Wisneski puts it, "me and a lot of other people like me."

Wisneski, 36, is an affable, solidly built man. He is the manager of two funds: W. L. Morgan Growth Fund, a conventional, long-term growth-stock fund, and Explorer Fund, an aggressive, maximum-capital-gains fund. Both are marketed and administered by Vanguard Group in Valley Forge, Pa., but are managed under contract by Wellington Management Co. in Boston. Wellington has been Wisneski's employer for the past 14 years -- ever since Wisneski, with one year at the University of Pennsylvania's Wharton Graduate Division under his belt, decided to stay on after a summer job, rather than finish his MBA.

From 7:30 to 9:00, Wisneski reads: reports from Wellington's research department; material from, or about, the companies he is interested in. "My biggest burden is reading," he says. "Fortunately, I'm blessed with a pretty good memory." At 8:30 or 9:00, he meets with Saul Pannell, his funds' associate manager, and with colleagues Mary Sprogell and Michelle Harris. All four compare notes about new prospects and updates an old ones.

W. L. Morgan and Explorer are both good-size funds, with some $620 million in assets between them as of early September. They have both grown a lot this year, partly because the bull market has helped pull their stocks up, and partly because a lot of new money has poured in. Morgan had $50 million in net sales in the first eight months of 1983, while Explorer attracted $136 million.

This new money is no problem for Morgan; Wisneski can, if he wants, simply double the fund's holdings in IBM Corp. or any of the other big companies it buys. Explorer is another matter entirely. The fund rarely buys a company with more than $30 million in sales, and it has to spend considerable time finding and researching such companies. One out of every seven or eight companies considered for purchase is actually visited. And only one out of about four visits leads to an immediate decision to buy.

From 9:30 to 10:00 a.m., Wisneski is on the phone to his trader. Where are the price opportunities today? The two plot their strategies: what to buy and, if necessary, what to sell. Whom to work with. How long to wait.

Once the decision is made to buy, the process may take four or five months. Explorer never buys more than 10% of a company, but even that much can push the market up prematurely. Some of the fund's stocks are so small that they are not even on NASDAQ's computerized listings. So the trader, Pat McCloskey, works closely with brokerage houses that are market-makers in the stock he wants, and he tries to accumulate a position over time.

From 10:00 on, Wisneski's schedule is a combination of things. Maybe half the day goes into managing the portfolio, checking prices, getting back in touch with the trading desk. The rest, Wisneski says, is "research in some form. "He talks to companies, their customers, their competitors, and other analysts on the phone. He reads still more. And he visits companies perhaps 50 a year.

Explorer is fundamentally a buy-and-hold fund. Wisneski professes not to be concerned with monthly or quarterly ratings of mutual funds; he looks instead at 5-to-10-year performance records. He turns over only about 20% of his portfolio each year.

Still, there are times when he has to sell. How does he know? One rule is mechanical: Whenever a stock makes up more than 3% of Explorer's assets, he begins to sell. "That means you miss a lot of the Haloids," he says, referring to the company that became Xerox Corp. "But you also miss a lot of the stocks that go from 2 to 200 and back again." Wisneski also sells when he begins to see a lot of brokerage reports on the companies he owns. "You bought the stock for growth," he explains, "and now it has grown. So you begin to peel it off."

Finally, Wisneski sells when he encounters what he drily terms an "irretrievable, fundamental shortfall." That is Wisneski-ese for a bad mistake. "We're usually patient with our holdings," he says, "and we try to allow for the variability that small companies can have. But sometimes there's no alternative. We're not venture capitalists, and we can't get involved in the company's management. So we vote with our feet."

At 6:00 p.m., Wisneski heads toward his home on Boston's South Shore. His 12-hour days don't allow him much time to polish his tennis game or go sailing; what time he does have he spends with his children, age six and four. "The personal activities can come later," he says with a laugh. "In 10 years, my kids won't want me around anyway."