Overpropped; What to do?
So, I purchased a boat a month ago and the prior owner has a 16 inch 3 bladed prop installed; unknown pitch. The boat has a Yanmar 4JHE and 2:17 gearing. The prior owner tells me the boat cruised well at 1800RPM, and it does, getting about 7kts, no black smoke. Max RPM while cruising is 2200RPM.
Now, I read that you should be cruising around 80% of your max rated RPM, in this case 3600. So, my questions is; am I doing any damage by cruising at 1800 RPM? What specifically?