* Cracked or damaged cylinder head gasket: This is the most common cause. The gasket seals the combustion chambers from the oil galleries. A crack allows coolant (which is mostly water) to leak into the oil. This is often accompanied by white, milky oil (emulsion) and loss of coolant. A minute of running might be enough to push a small amount of coolant into the oil.
* Cracked engine block: Less common than a blown head gasket, but a crack in the engine block itself can also allow coolant to mix with the oil. This is usually a more significant problem resulting in substantial coolant loss.
* Failed oil cooler: If your engine has an oil cooler (common in marine engines), a leak in the cooler can allow coolant to enter the oil system. This is more likely to show up as a gradual increase in water in the oil rather than immediately after starting. However, a sudden large leak could cause this.
* Improperly installed or damaged raw water impeller: While less likely to directly contaminate the oil, a badly damaged impeller can allow water to be sucked into the engine through other pathways, potentially making its way into the oil system under high pressure.
What to do:
1. STOP using the engine immediately. Further operation will likely cause significant damage.
2. Check your coolant level. A significant drop indicates a leak into the engine.
3. Check the oil for milky or cloudy appearance. This is a clear sign of water contamination.
4. Have a qualified marine mechanic inspect the engine. This is crucial to determine the source of the leak and avoid further damage. Do not attempt to diagnose or fix this yourself unless you have significant experience with marine engines.
The speed at which the water appeared in the oil (after only a minute) points to a serious and potentially expensive repair. Prompt professional attention is vital.
