Shares of MarineMax ( HZO) plunged 17% Monday after the boat retailer slashed its 2007 earnings guidance. The company now sees earnings of $1.40 to $1.50 a share for the year ending Sept. 30, down from its prior projection of $2.05 to $2.15 a share. Analysts polled by Thomson First Call have an average estimate for earnings of $2.11 a share. "Based on recent industry reports, it is clear that the marine industry is experiencing increased softness caused by uncertainties in the macroeconomic environment, which adversely impacted our results," the company said. For the recently ended first quarter, MarineMax estimates a loss of 20 cents to 25 cents a share, with revenue of about $235 million. Analysts project a loss of 6 cents a share and revenue of $234.3 million. The company said that first-quarter same-store sales increased 14%, but product incentives, higher marketing and promotional costs cut into margins. Shares of MarineMax were trading down $4.15 to $20.62.