What is a typical sign of coolant leaks in a marine engine?

A typical sign of coolant leaks in a marine engine is the presence of black soot around the exhaust manifold. This occurs because when coolant leaks into the combustion chamber, it can cause a rich fuel mixture that results in incomplete combustion. The byproduct of this incomplete combustion can create black soot, which may accumulate around the exhaust manifold area. It's important to regularly check for such signs, as a coolant leak can lead to more severe issues like engine overheating or damage if not addressed promptly.

Other options, while they may indicate different problems, do not specifically point to coolant leaks. For example, cloudy exhaust fumes could suggest issues like oil consumption or a rich fuel mixture due to other reasons, while bubbling in the fuel tank may indicate a fuel system problem. Unusual noises from the engine could be attributed to friction, wear, or other mechanical issues rather than specifically pointing to a coolant leak. Each of these signs reflects distinct issues requiring different diagnostic approaches.