There are many potential causes for a boat not to steer straight. One common issue is with the boat's rudder. If the rudder is not aligned properly, it can cause the boat to veer off course. Another possibility is that something is obstructing the propeller or rudder, such as debris in the water or a line wrapped around the propeller. Additionally, strong winds can push a boat off course.
If you're having trouble steering your boat straight, it's important to first check for any obvious issues that could be causing the problem. Once you've ruled out anything obvious, you can then begin troubleshooting other potential causes. If you're still having difficulty, it's best to consult with a professional mechanic or captain who can help diagnose and solve the problem.