I assume you've got the 430 Lincoln engine.If you have only 3-4 psi fuel pressure, that's too low at WOT.You should have at least 5-6 psi .BBF's are thirsty blocks.4200RPM is low for that engine.The 430 is a 10:1 comp short stroke engine and should rev at least 4700. A 16' Tahiti should be able to run 60MPH with a hotrod lincoln wink definitely !