Four men boarded a wooden motorboat in April 2007 and headed out into the main channel of Smith Mountain Lake, where high winds whipped the surface into 2-foot waves. Only two of them survived the trip.

The estates of the two men who died have each filed lawsuits seeking $10 million in damages against the owner of the 33-foot Hacker Craft antique replica and several companies involved in the boat's manufacture and maintenance.

An investigation by the Virginia Department of Game and Inland Fisheries found that a combination of high winds and a malfunctioning cooling system that caused the inside of the boat's hull to fill with water made the boat capsize and sink on April 4, 2007.

The owner of the boat, Walter Curt, was steering it at the time it flipped over. He and a passenger, Dennis Zimmerman, were rescued soon after by a father and son passing by in a runabout. The remaining two passengers, Richard Smith, 64, of Moneta, and David Reynolds, 44, of Grottoes, drowned in the chilly waters. Reynolds' body wasn't recovered until four months after the accident.

Smith Mountain Lake lawyer William Stanley, who has filed three lawsuits in Bedford County on behalf of the Smith estate, called the tragedy "a perfect storm of negligence" by a number of parties that "resulted in the deaths of two fine gentlemen."

Roanoke attorney Sean Workowski, who filed a suit in Franklin County on behalf of Reynolds' estate, declined to comment in any detail on the suit Tuesday.

A key difference between the two sets of lawsuits involves their treatment of Walter Curt and his companies, Emerald Isle and Beryl Isle.

Both sets of suits accuse Curt of steering the boat in an unsafe manner and operating in unsafe conditions that he lacked the experience to handle. The Reynolds suit further alleges that he failed to recognize that his boat had a dangerous defect.

The Smith suits list him among the defendants targeted for $10 million in compensatory and $350,000 in punitive damages. However, the Reynolds suit leaves Curt and his companies out of the list of defendants from which the estate demands $10 million in damages.

Curt's attorney, John McGavin, declined to comment in detail on the suits. "It's a very unfortunate accident," he said. "We just don't believe that Mr. Curt caused or did anything that contributed to the incident."

Both sets of lawsuits name as defendants Hacker Boat Co. Inc., the maker of the boat, and Buck Algonquin Co. Inc., the manufacturer of the cooling system part that malfunctioned. Attorneys and officials for those companies could not be reached for comment Tuesday.

The suits also name Shoreline Marina in Bedford County, which serviced the boat the winter before the accident. At the time the marina was owned by Mark de Tournillon Sr., who six months earlier had been sentenced to 15 years in prison for causing a boat crash that killed a Moneta couple. The marina has since been sold to new owners and renamed. Stanley said the lawsuits do not affect the new owners.

David Hart, attorney for Shoreline Marina, declined to comment on the suits.

According to the lawsuits, Curt purchased the boat from Hacker in fall 2006. Before the boat was placed in storage, Curt had it "winterized" by Shoreline Marina, a process that involved putting antifreeze into the boat's cooling system. In March 2007, Shoreline Marina "de-winterized" the boat so it could be used on the lake.

On the day Curt took his three passengers out onto the choppy water, a leak in the cooling system allowed water to start collecting inside the hull of the boat, the suits say.

The Smith suits further assert that as Curt negotiated the lake's curves at a speed of 30 mph, he noticed the boat's steering wasn't responding when he tried to turn. He then attempted to slow the boat down, but instead of pulling back the throttles for both the right and left engines, he pulled back the throttle for only the right engine. The boat lifted and rolled because of the maneuver, the water accumulating inside the hull shifted, and the boat flipped over and sank, the suits state.