How much horsepower does a 4 cylinder 3.0 liter mercruiser have?

There's no single answer to how much horsepower a 4-cylinder 3.0 liter MerCruiser has. MerCruiser 3.0 liter engines (which are actually 2.5 liters in displacement, a common point of confusion) came in various configurations over the years, each producing different horsepower outputs depending on the specific model and year of manufacture. The horsepower could range from approximately 135 to 140 hp, but it's best to consult the engine's specifications or a MerCruiser parts and service manual for the exact horsepower rating of a particular engine.