Hey, we all could use a little more cash in our pocket. What you don't want, though, is more cash in your stock fund. Determining how much is too much, though, can be tricky business.

Certainly, there are sound reasons for keeping cash in a stock fund. Indeed, the average U.S. stock fund has 5.1% in cash, although anything less than 10% is within the realm of "normal."

Bad Trends in the Industry: Not only is performance off -- you may not even be able to find out who's in charge of your fund.

Reverse Engineer Your Mutual Fund: Here's how to analyze a portfolio to uncover a manager's strategy.

10 Questions With Prudent Bear Fund Manager David Tice: Skepticism has never been so profitable.

A cash reserve gives fund managers a cushion that can ease the purchase of a new stock or additional shares of an existing holding.

Cash can also ease the sting of high redemptions, which can spell trouble for funds, especially if it means managers are forced to sell holdings they believe in. "That can be a sensible strategy," says Christine Benz, editor of Morningstar FundInvestor.

But too much cash in a stock fund means that portfolio managers need to take bigger risks with the invested portion in order to garner returns equal to (or better than) their benchmark index. That's why the driving philosophy of some fund families, such as Rydex Funds or Turner Investment Partners, is to stay 99% invested at all times -- even the universe average of 5% cash poses hazards.

"We don't want to have to take that extra risk on how we would have to invest a customer's $95 to get them the return they expect on a $100 investment," says William Flaig, senior portfolio manager at Rydex.

Then again, such strict policies can be somewhat limiting. A cash cushion, after all, is particularly helpful in funds that hold several illiquid shares -- as is the case with small- or micro-cap funds and some foreign funds. Companies with small

market capitalizations -- as well as some foreign stocks -- don't trade as frequently, which means that divesting a large holding could drive the share price down. If there's cash on hand, a fund manager could avoid painful sales.

In order to keep to its policy of full investment, Rydex offers only stock funds with large-and mid-cap holdings, which are easier to get in and out of.

Fund managers that have strict buy and sell criteria -- such as value managers Curtis Jensen at

Third Avenue Funds

and Wally Weitz at

Weitz Funds

-- often find themselves holding higher-than-average cash positions. "Some value managers simply can't find stocks that they think are cheap enough," Benz says. "Particularly in small-cap value, which has had a couple of great years."

The cash position in Jensen's small-cap value fund, for instance, has vacillated between 15% and 30% over the past year.

Generally, though, investors should question the manager if a fund has more than 10% in cash. Too much cash will not only cause a drag on returns within the fund, but also in your overall portfolio. After all, you already know to beware stock duplication among funds; above-average cash holdings in more than one fund can throw off the asset allocation of your entire portfolio.

So keep an eye on the cash position in your funds. If you trust the manager and expect him or her to deploy the cash within a few months, there's no need to bail. But if the manager seems stuck, and maintains a high cash position for several months without closing the fund, think about shopping around.