My starboard engine is burning a lot more fuel than the port. Went out yesterday with full tanks, came home with one empty and one on half. It doesnt smell excessively rich, idles well, but starboard is down on rpm a little. The engines are in synch up to 3000 rpm, but when I go wot the port is at 4500 and starboard at 4000. Both engines have fresh tune ups, carbs are holley 800 double pumpers. No fuel in oil either.

Could the fuel pump be weak on the starboard, or maybe a clogged filter? That would explain the lack of rpm, but not the fuel consumption.

Hey bud, did you ever figure this out? Both my engines are running awesome but the port motor uses about 25% more fuel then the starboard. Can't figure out why..... Fresh fuel filters, rebuilt carbs all the way around. Last time out filled both tanks to the top. Today refilled, starboard took 38 gallons, port took 51 gallons. Can't figure it out???

Also just got boat back from the shop, both leak downs, and valve lash were excellent on both motors. They are both very healthy and in great shape. What would cause this?

Hmm I also noticed my port eats more fuel.

One thing I have noticed is when boat is just floating in neutral motors not running, my port prop is significantly harder to spin than the starboard prop. Could this extra friction/load make that much difference?

^^^ Friction dose take more HP to over come, and HP takes fuel. Sounds like you have a winter project of a drive rebuild in front of you, is my guess.

My starboard engine uses more fuel than port. I never really measure the difference, but it is 5-10 gallons different usually (from my memory).

I assumed it was due to me using the starboard drive more (docking, trailering, etc).

Almost every boat I've been on does this, some more than others. My hawk with one tank 2 pickups the stbd dies about 2 min before the port lol so I'm guessing I have different pick up heights

Are the builds the same on both engines? have you checked O2 readings? Mine are within 1/2 gal on refueling....But I'm EFI

My original post was from 8 years ago lol. I think the problem was ignitions. I replaced both distributors in those engines (they had points), and ran much better.

Lots of variables on why one engine might burn more fuel. Slight difference in prop pitch (very common in ssm props), idle mixture settings, jetting, ignition timing, one engine having a p/s pump, etc.

Rob, you really need to get those 02 sensors going, and see whats up. From there we can make some changes with carb's.