The 33-year-old, who also won silver in Atlanta in 1996, came into the event below his optimum weight and lacking Finn-specific fitness and claimed he would satisfied with a top 10 finish.
British sailors hold medal positions in four more of the 10 Olympic classes going into Saturday's finale, two years before the sailing events of the London Olympics are held at the same venue.
Olympic champion Paul Goodison is second, eight points adrift of Australian Tom Slingsby in the Laser class, while Athens bronze medallist Nick Dempsey is equal on points with the leader of the men's RS:X windsurfing class.
Brits second in Paralympic classes
In the 49ers, Britain's Stevie Morrison and Ben Rhodes, the 2007 world champions who came ninth in Beijing, are in third place but level on points with compatriots Chris Draper, the double Olympic medallist, and his crew Peter Greenhalgh.
The two rival teams, competing for the one spot in each class for Team GB in 2012, are three points adrift of the second-placed boat from France and still capable of ousting Australians Nathan Outteridge and Iain Jensen at the head of the fleet.
"What a tough day, so frustrating," said Rhodes after placing 13th, ninth and 16th in their final three qualifying races on Friday. "We were fighting two different winds. Hopefully we can hang on to a medal."
Dave Evans and Ed Powys also qualified in eighth but Britain's 2009 world silver medallists John Pink and Rick Peacock failed to qualify for the 49er medal race, finishing the regatta in 14th place.
Luke Patience and Stuart Bithell are also third in the men's 470 class, 15 points off first and 13 clear of fourth-placed Nic Asher and Elliot Willis, Britain's two-time world champions. Ben Saxton and David Kohler will go into the medal race in eighth place.
Windsurfer Bryony Shaw is fourth in the women's RS:X class, two points off third but with a pair of Italians breathing down her neck.
In the Finn, Ed Wright has a chance of making it a British one-two-three. The winner in Weymouth 12 months ago is fifth but only three points adrift of Frenchman Jonathan Lobert in third place.
But Olympic Star champions Iain Percy and Andrew Simpson, who have also been focused on Team Origin duties, struggled after breaking their rigging earlier in the week and are a distant sixth.
"We chose the wrong side of the course and pushed too hard to get back into the regatta," said Simpson after the pair came 10th in the final qualifying race on Friday.
In the women's 470, Penny Clark and Katrina Hughes are fifth but just two points adrift of third place, though double Olympic champion Sarah Ayton and crew Saskia Clark failed to qualify for the medal race, finishing 14th in their first season together.
"It's been a massive learning week for us," said Ayton.
"We're two years out of the Games and we've got a lot of work to do over the winter but we'll come back stronger.
"Even though our results haven't shown it we've come a long way this week. We're well on track in the bigger picture."
Lucy Macgregor's match-racing crew lost 3-2 to USA's Anna Tunnicliffe in the quarter-finals.
In the Paralympic classes, John Robertson, Hannah Stodel and Steve Thomas claimed silver after completing their 10 races on Friday.
Fellow Britons Alexandra Rickham and Niki Birrell also won silver in the Skud class.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.