Prop, pitch and jackplate setting - 2004 521 250xs - PLEASE ADVISE

I have a new to me 2004 Ranger 521 DC with an 04 250xs with a 6" manual jackplate. I'm getting similar speed with a somewhat dinged up 27 Tempest (5100+/ RPM - 65 MPH) with a new 25 Fury @ 5400 +/- RPM - 65 MPH. I've been told this setting should do 72-74, but I don't think I've ever hit 68...

I haven't measured the plate height yet, but I've played with it from the factory setting down 1", and back up 3/4", yet minimal change (best 1/4 below factory setting). Does anyone know the perfect prop, pitch, jackplate setting and plug hole diameter (in prop)?

New plugs, Quick Kleen treated, always 91-93 octane, just replaced fuel lines (almost 30% clogged with the old liner - but little different top end noticed = much better hole shot), new temp sensor, I've run a couple cans of Sea Foam through both tanks and no significant improvements. I'm tired of dumping money into the boat with the hopes it'll make it hit 70+.. All advice appreciated as I'm tired of throwing money away.

When you replaced the fuel lines did you do anything else to the fuel system? I don't think you will ever see 72. You may want to go to the Mercury 3.0 L motor board and ask Don about your motor problems. There is a list of things to do when you change your bad fuel lines including all the filters. Get your serial number and he can look it up and will know more about your motor.

You need to try a 25 Tempest and start at 3.5" BTP.

-Eli