Just got a 78 macgregor 21' how do i operate the retractable keel? just lower it or what? Is there something that locks it in place when down? or does it just hang there? The trailer has what looks to be an extendable toung if that makes any sence. it extends about 8-10 ft I dont think its been moved in years any info on how its suposed to work i know theres 1 bolt holding it togeather