[Chris Burkard]

Flo-Scans are notoriously inaccurate and their accuracy is highly dependent on the installation. 3000 to 3200 RPM is approximately the sweet spot for those engines with that hull on a calm day. If the engines are tuned properly and the bottom is clean and you have the correct props, you should be getting about .87 MPG. It is extremely unlikely you are getting over 1 MPG. I have never seen it in a boat that size with those engines. If you run slower than 3000 RPM, your MPG will drop as the hull drops lower in the water and comes under more drag. Faster than 3200 RPM and your mileage begins to drop as well.

Now, .87 MPG is under ideal conditions. If you run into 14 knot winds with a 3' swell, your MPG may drop to .70. If you are running in 5' swells with a bit of chop, your MPG may drop to .5 MPG. If your props or bottom or dirty, you will burn more fuel. If your engines are not tuned properly, you will burn more fuel. If you have the wrong props, you will burn more fuel. If you overload the boat with extra weight, you will burn more fuel.

The other issue is the 33 never came with 8.1L Crusaders. The original engines were 7.4L Crusaders at 320 HP each. The 8.1L engines are likely the 385 HP versions (the 8.1L is also offered in a 425 HP version) and have a completely different torque curve. What propellers do you have? The original props for the 7.4L engines will not work for the 8.1L engines. Wide Open throttle, what RPM are you achieving? Those engines should turn between 4350 and 4550 with a fully loaded boat. If they don't turn up, you likely have the wrong propellers and are overloading the engines burning extra fuel.

Did you survey the boat before you purchased it? It sounds like you have quite a few issues that should have been discovered during the survey.

E-mail me and I will send you a performance report for a 31 Tiara with the 8.1L engines. It is not a perfect match as the 33 is wider and heavier, but it will give you a general idea of what the fuel burn should be at various RPMs.