I have been running a 1985 21' open bow Crusader with a 454 W/ mild cam and a Berkley jet for the last 5 years. I am wanting to upgrade carburetors as my current Holley 750  with vacuum secondaries has some stripped screws and seeps after many rebuilds.  My question is should I stick with the exact upgraded version of my old Holley 750 with vacuum secondaries or should I move to a different carburetor with manual secondaries?  The majority of my boating is cruising between 3500 and 4000 rpm.