I have a 1988 Ski Nautique with a 351 Ford. Engine has 700 hours and has been serviced regularly. Put boat in H20 today and after starting, the oil pressure gauge was bouncing erratically from one end to the other. Fearing a major problem, I shut the motor off after about five minutes (did not over heat-temp normal). Pulled the oil dipstick to find chocolate milk instead of the new oil that was changed at the end of last summer. No need to winterize for the temp does not get below 32 degrees. The boat has been used twice this year for a total of about three hours. Everything ran fine. What is going on? Suspect the manifolds need to be replaced, but I'm not a mechanic and not very knowledgable about the engine. Why did the oil pressure gauge go ballistic? Can H2O get into the block by other means? Have I damaged the motor in any way? What is my next step?