Tiara sent me a number of documents when I bought my 3300 Open which included a graph with the RPM range, speed and GPH during its initial test run. If I remember correctly, for my boat is was around 3000 RPM, right before all 4 barrels kick in. You can try to email them to see if they have it for your boat at cr@tiarayachts.com and put the HIN # in the subject line. This can change a lot over the years as there are many variables like weight, bottom paint condition, prop wear etc. You should be able to hear when the 4 barrels kick in and then throttle back some, most likely your current sweet spot. If you want to know for sure, I would install a fuel flow meter to check yourself. A option that I would like to install at some point.