[jmdegraff]

Hello,
I'm new here, relatively new to bigger boats, and not a mechanic. The starboard engine on my boat is using more gas than the port engine, which is causing the boat to list to port. Starting with two full tanks late last year, the port tank is nearly 3/4 full whereas the starboard tank is just over 1/2 full. Both engines seem to run normally. There is no crossover valve to allow gas to flow from one tank to the other; each tank feeds the engine on the same side.

What are the most likely causes for the difference in how the two engines are using gas? I'm hoping it's an easy adjustment or fix.

Jim

[penneyma]

Are you certain there's no crossover? On my '95 3500 express the fuel crossover is on the forward engine room bulkhead.

Did you fill the tanks simultaneously or one, then the other? Remember that the latter will actually make your boat list while filling and the first tank will naturally be less full than the second (unless, of course, you went back and topped off the first tank).

If you're really burning more on the MPIs, it could also be that one motor is pulling more load. Do you have a synchronizer? Have you verified that your tachometers are accurate? If you've been pushing one motor even a few hundred RPM more than the other, that'll create an imbalance in how hard it's working and definitely result in a higher fuel burn.

Just some thoughts. Are you noticing a particularly rich fuel smell on one side's exhaust?

[hiccup]

First, I would fill the tanks and confirm the gauges are accurate--fuel tank gauges are notoriously inaccurate. The list may or may not have anything to do with tank imbalance.

Do you have a generator? Do you use it a lot? That is going to draw from only one of the tanks and could explain the difference, although 1/4 tank is a lot for a generator to use.

Because you have MPI engines, you have access to fuel burn info. Compare burn rates at different RPMs. Reset the total fuel burn and keep track of it, comparing the 2 engines to one another. If one engine is in fact burning 2x as much fuel as the other, then something is definitely amiss, and you may consider calling a mechanic.