fit the appropriate size screw driver in the slot, the biggest one that will fit, hold it steady and rap the end of the screw driver with a hammer, once twice three times, then twist free, remember righty tighty, lefty loosey. If this fails, spray with penetrating oil and let sit for a day, then repeat the same steps. Good luck.
FreeBee.... If you're not using one, go to Sears (or whoever) and purchase a "Impact Screwdriver", a tool that you'll use many times and wonder how you ever got along without it.
Free Bee - Follow Joe's advice. I used the impact screwdriver last weekend for the same purpose. When you go to put them back in make sure that you use new nylon bushings. My drain plugs were frozen because I had O rings instead of the nylon. The impact loosened them right up.
Free...<br /><br />You might want to insure that the opposite side of the lower is supported while you strike the impact driver to protect the somewhat fragile aluminum castings.
SlowBoat..... No offense intended here, just being informative. No need to support the other side of the unit, even on the smallest hp engine. Those units are sturdy and the impact screwdriver can really be whacked with no damage being encountered.
