Visit Home Depot and pick up a one gallon can of WD40 for about $10. Fold a cotton towel so that you can wrap it around the manifold and press it up against the engine. Hold it in place with plenty of duct tape. Make a drip tray from several thicknesses of aluminum foil and place it beneath the towel. Soak the towel with WD40. Telephone Catalina to order a new manifold. You may wish to ask them how many bolts are used to attach the manifold to the engine so that you will know whether you have gotten all of them out. During the three weeks it will take Catalina to fabricate a new manifold, visit the boat frequently and keep the towel soaked with WD40. Re-use the stuff in the drip tray. By the time the new manifold arrives, the WD40 should have finished its work and the manifold should come off. When you do the re-assembly, give the bolts a good dose of waterproof lithium grease from a spray can. If you ever have to remove them again, they'll practically leap out. BTW, hang on to the old bolts. New ones don't come with the manifold. Just use some new split ring washers to keep the old bolts from from vibrating loose.
