Fuel efficiency.

[xp640]

I have quite a standard RIB.

6.5m Rib from rib-x
150hp Honda 4 stroke (2007)
200 litre fuel tank.

get-me-home 5hp reserve honda engine
20 litre reserve engine fuel tank.

a rear bench, 2 double jockey seats, a big console

added to a Hull weight of 380kg....

.... Can anyone give me an idea of expected fuel consumption. The fuel gauge is very vague and I was hoping someone might know ballpark figures.

What would the most fuel efficient speed be?

Figures with 2 pax (160kg) and 10 pax (800kg) would be appreciated in both slight and moderate waters.

[Trailer Bloke]

This totally depends on how you run it

We on average burn approx 20 l/h running fairly fast 5500 rpm

If you throttle back to 5000 you see about 16 l/h

One of our commercial drivers on this forum is brilliant his boat consumes 2/3 of the fuel of the other boats.

He doesnt go over 5000rpm as this is when they really guzzle

[Nick Hearne]

I would say at around 25 knots you would be looking at 1 Lt per mile!

[Millermob]

On our Avon 620 with Honda 150, we used to average 16lph at roughly 22 knots in calm / moderate seas with 5 on board - equated to just over 4000 rpm.

Not sure about figures with extra weight.

This was running a 4 blade adjustable prop!

[BruceB]

There are a couple of Argyll folk on here but it is a big place. Which part do you hail from?

[xp640]

port appin / loch creran.

[stepheneyre]

hi
just get the rib on the plane so just the back end is in the water this i feel is the most fuel effective.
also depends on the prop pitch and the boat load , just trial and error to get the rib just on the plane any faster and you just burn more fuel but get there quicker
its like doing 55 mph on the motorway too slow but 70 is useing more fuel
thanks
stephen

[Hightower]

That size of RIB and engine combo I would factor at least 1mile/litre as a ball part figure and then deduct 20% for a safety factor untill you get to know your RIB. So for a 200litre tank that would be a 200 mile maximum range less 40 miles....So go no further than 160 miles on a full tank.

One thing to remember is to gauge how much fuel gets pumped into the tank as some fuel tanks say 200 litres capacity but might hold less than this because of poor installation. My BWM would fill to the brim whilst filling on the water but when on the trailer the nose was higher and couldn't get full capacity because an air trap would develop at the front of the tank, if I wasn't carefull push the fuel suddenly up the filler hose with expected results.

[Limey Linda]

Originally Posted by stepheneyre

hi
just get the rib on the plane so just the back end is in the water this i feel is the most fuel effective.
also depends on the prop pitch and the boat load , just trial and error to get the rib just on the plane any faster and you just burn more fuel but get there quicker
its like doing 55 mph on the motorway too slow but 70 is useing more fuel
thanks
stephen

This approach may not always be the correct one for best economy. Most engines are at their most economical at 3500-4000 rpm. If you read enough engine/boat test reports you will that this is so. Some times it is more economical to run at 4000 than 3500. Remember the faster you go the less hull in the water up to a point. If you can find that sweet spot then that is usually the most effecient. Of course sea conditions have a lot to do with it.