[Double Z]

This is based on your numbers. If your manual says the max RPM (redline) is 3800, don't exceed it. Are you quickly hitting the rev limiter or does it take a while to get up there? Can you spin through the props if you give it too much throttle too quickly? I demo'd a Fountain that did that with a 300hp Yanmar and a single prop. That motor pushed right past the prop and cavitated.
At what rpm does your motor make peak torque and what rpm does it make peak HP?

How does the motor "feel" at lower rpms? If you start moving, and get to the point just before coming up on plane, what happens when you give it more throttle? How about doing the same thing while loaded with full fuel and gear, going up the back of a large swell? Putting in a pyro would be a great place to start with finding out if your motor is happy or not.