At the end of Hookie Day, Both of my 525 Mercury engines showed milky oil above the full mark. Pulled both motors @ SOS Marine, & took them to Don @ Motor Machine. Don pressure check all four headers before tearnig down the motors, all four header were cracked. I called CMI & Mercury Racing to check if this was something they new about. Come to find out, they new about the problem, and redesigned the CMI Sweep Headers for the 525's motors. Mercury Racing offered to sell me new Headers through one of their dealers at $8,000.00 a set. I'm aware that parts wear out, that's why we do preventive maintance every winter, but if I would have known about this, I might not be rebuilding both engines. So DLB check those spark plugs, and look for moisture, and pressure check your CMI Headers. Please, check my story for yourself, give them a call like I did, it might save you some money.