Mercury 90 Four Stroke Fuel comsumption

[JABS]

I have a question on Fuel Consumption.

We were out at the weekend. Ribcraft 585 with a 90 Four stroke Mercury. Three up, full fuel tank, little gear.

We travelled about 35 nautical miles. Half was in good conditions at around 20 to 22 knots.

The return was very lumpy. We were unable to maintain more than 8 to 10 knots.

Journey time was nearly three hours.

The fuel burn was just over 40 litres.

Is this what other ribbers would expect?

I was expecting to be able to average maybe 0.75 litres per mile. This is way more that that!

Would appreciate some input from fellow ribbers.

thanks.

[Hightower]

To do half your journey at 10 knotts is going to hurt fuel economy as you'll be at displacement speed. The 22 knotts cruising is more in keeping with 1.2nm/litre I used to get with my f90 merc.

So yes, I might expect your fuel economy to be .875 nm/litre.

[JABS]

Thanks Andy,

I had expected roughly 0.75 litres per NM. That ties in well with your experience.

I can live with that.

But then I'm not very green anyway!

Tony.

[alystra]

Year 2000 90hp. 1 pob full tank, dinghy, aux o/b, lots of anchor chain and gear. Average over a season 1.6 miles per litre at 3600 rpm 23knts. cruising speed. Rather more if I have to waggle the throttle a lot. More too if I'm at displacement speeds.

I'm beginning to do a lot of 'messing about' among rocks and stuff and I'm thinking it would be more economical to use my 3hp Johnson aux for slow speed, though manoeuvrability is a bit dodgy.

[matt h]

humber 5.3 ocean pro, 3 persons, 90 Mariner f/s (same engine), 50 litres and could not get around the isle of wight, needed another 3 litres,

[JABS]

A big thank you to everyone!

I shall be happy with 0.75 to 1.0 litre per mile, than.

How big is my carbon footprint?

Not as bad as some who appear here...

Tony.