Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of industrial-pumps purveyor Colfax (NYSE: CFX) slumped as much as 13% today as investors voted with their feet against a planned merger in the making.

So what: On Monday, Colfax bid $2.4 billion to acquire competitor Charter International PLC. Yet at that price, Colfax says it won't earn a return on its investment for at least three years and may need as many as five years for the deal to become accretive.

Now what: Colfax's bid works out to 914 British pence per share of Charter, trumping a lower 850 pence bid from turnaround specialist Melrose -- a lower bid that Charter has twice already rejected. There's no guarantee that Charter shareholders will be more receptive to Colfax's bid -- indeed, Charter shares rose only as high as 858 pence on the offer. But already Colfax investors seem to be looking at this like a done deal and punishing Colfax for overpaying. When you consider that Colfax shares already cost 30 times earnings, that earnings growth was supposed to average 15% per year before the buyout, and that by its own admission, Colfax says buying Charter will hurt earnings for years to come ... I can't blame investors for bailing.

Will investors regret abandoning Colfax in its moment of "triumph"? Add it to your Watchlist and find out.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.