What should be compression on A 150 HP outboard be?

For a 150 HP outboard motor, ideal compression readings typically range between 100 and 130 psi per cylinder, but this can vary based on the specific engine model and manufacturer specifications. It's important that all cylinders show similar compression values, with no more than a 10% variance among them for optimal performance. If compression is significantly lower than the recommended range, it may indicate engine wear or other mechanical issues that need addressing. Always refer to the manufacturer's service manual for precise specifications.