according to Yanmar.
The best speed to run your engine at is 70-80% of the max rated RPM which is 3600 rpms. This would put you somewhere in the 2500-2900 range. It is fine to run you engine up to the max running rpm (3400) for 10-15 min. as long as you are not overheating. You engine should be able to reach this 3400-3600 rpms if everything is in good shape (clear mixing elbow, clean bottom, proper prop etc).
