OK, so it is VERY important to know if you have the 4-banger or the V-6 version AND what the overall gear ratio is! Note that Suzuki, in your vintage range, has a 1.1-to-1 reduction gear IN THE POWERHEAD plus another more typical reduction in the lower unit...not sure about your specific motor. Be sure to check your specific model of motor because the gear ratio that may be on the lower unit could be misleading.
As an example a friends 2024 200 Suzi 4-banger has an OVERALL ratio of 2.5-to-1, as do the recent 150hp motors. As a result, the very best prop (so far) for his 22' Bentley is the Solas 15" x 21p that produces strong acceleration and a light-load top end of 44 (with six adults, full fuel and top up the speed is about 37-38). Running very light that prop will hit the rev limit, but does not with a typical load.
A surprising number of people don't know about the gear reduction in the powerhead and then mis-identify the actual gear ratio and wind up with props that have neither enough diameter nor pitch. In any event, a number of people have found the Reliance line of props to not be a good match for their pontoon needs. That said, the numbers you are reporting indicate there may be something other than just a prop mismatch, you should have the power to run easily more than 33 even at only 5700 RPM. Are you using a GPS and does the tach seem to be operating normally?