So my boat thermo locked and never mixed the oil and water but it did have about 1/2 quart of water in the bottom of the pan . I pulled the plugs to do a cylinder test to find where it might be bad and water came out of 3 and 6. It is a 4.3 mercruiser, do I need to do any other checks or just figure both head gaskets are blown and start tearing it down?