454s with Holley carbs questions about carb operation

I'm trying to better understand the operation of and tuning of the carbs on my older 454s. The carbs are SAE J1223, model 9015-1.
Research tells me they are marine carbs 750 cfm designed for electric choke and (vacuum secondaries?).

Engines are running ok but starboard motor seems really rich and my fuel consumption on the starboard side seems to be 2x the port side. I just purchased this older project boat about 6 months ago and have been working out things as we go. I have not attempted to put the boat on plane yet, but have done a few lengthy harbor cruises at about 1400 rpms. The boat is a 1976 Jeffries flybridge (fiberglass) it is 32' long and weighs 18,000 lbs. I know the weight from scale on crane during haulout for bottom paint.

According to my fuel monitoring (based on tank dipstick and known distance traveled) I am afraid the starboard side has been burning close to 2 gallons/mile, but the port side something less than 1 gallon/mile. No smoke or other symptoms except some grayish smoke at start up on the starboard side that clears when warmed and idled down. It does not reappear once warm.
I suspect I have a timing issue on that motor and will check it out. But in looking forward to the day when I take the boat up to 3000 rpms on plane, I am curious about fuel economy vs tooling around at 1500 rpms. Can you check when secondaries are opening while sitting at the dock and looking into carb as rpms are taken up? At what rpms should secondaries open? Thanks for any help.

the fuel consumed will vary with the condition of the engine, its state of tune, and the load seen...you've got a substantial load from just the hull....so set expectations accordingly.

For the most part; fuel consumption will vary with rpm (not always linearly) so slower usually = less fuel consumed. Also, not that your carbs (model 4160, BTW) came with a 'generic' (usually means on the rich side) calibration, so there may be benefits to be had there.....I don't believe you will see the secondaries open in a 'no-load' (at the dock in neutral) condition. As far as when they open, you can tune the carb to determine that....the short answer is they need to open when the primaries no longer supply adequate fuel.....if the gear ratio is optimal and the props are correct, you should be able to cruise on the primaries up to 3000 rpms....