I am new to boating. Bought a 1988 crestliner with the OMC 3 litre engine. I took it out ant the head gasket blew. The mechanic told me head was warped and sent it out to be machined. I got the boat back and took it out for a test run and the gasket blew again within 5 minutes. Took it back to the mechanic and he looked it over and told me that the block may be warped and had to do some sanding or something to it. He told me that this should fix the problem. He also told me that it is expensive to machine the block as the engine has to come out along with the pistons etc. He did not charge me any extra for this sanding telling me it should be fine now. I took it out today to test it and again the head gasket blew. Not sure what to make of this. Can an engine block warp or is this mechanic giving me the gears. It's an old boat and may not be worth an expensive fix.