Generator Usage

Maybe he missed a decimal place. 1.8 sounds closer.

Yep, 1/2 half gallon per hour / half load / around 1.8 L.
Sea Gull had it.

Buy a 63 and run it a while. Or just buy an Onan 17.5. Those who answered you were serious and far more on target. Why do you have to prove anything to anyone?

Here's a general generator fuel usage chart. I've found all modern generators do better than the chart.

http://www.dieselserviceandsupply.com/Diesel_Fuel_Consumption.aspx

Here's a Cummins chart, but it doesn't include small units.

http://www.powersystems.cummins.com/_literature_98391/Generator_Rental_Specs_and_Sizing_Charts

They show the 35kw at 3/4 load uses 2.2 gph.

We have a 21.5 kw on our Sunseeker (actually have two but only run one at a time) and use less than 1 gph on average.

Does the 18L/hour x engine hours match fuel usage? If so, you may have another problem.

The question is if he is stealing fuel, doesn't understand math, or there is a problem onboard that he also doesn't understand?

How is he figuring out the fuel use of the generator? I do it when I top off both tanks and measure the difference, since the genset runs off only one of my two tanks. But this only gives a rough estimate, given that there can be slight differences in fuel use of the two main engines and differences in what "full" is.

Many gensets can draw from either tank and return fuel to either tank. Check that you are returning fuel to the same tank as you are drawing from. This could cause the inequity that would cause him to think the genset is using more fuel. Also, try switching the fuel feed/return to another tank. The would indicate extra fuel being drawn by one of the mains.

To shut him up install a fuel flow meter

To shut him up, don't let him touch your boat again.

We have a pair of 18kw Northern light on the boat I run and we burn on average 1 to 1.5 GPH.... 4 to 6 liters an hour.

There is no way you could burn 18 LPH in a generator that size without a big black cloud and a fuel slick on the water, either woudl either land you in jail or result in some tree hugger riot.

The "chap" managing the boat obviosily believes that boat means bend over and take it.

He either doesn't know what he's doing and talking about or he's intentionally fabricating a story, thinking your stupid. So incompetent or dishonest. Doesn't really matter which, I'd be going elsewhere.