fuel consumption in 22' speedboat

[VvrooomM]

Looking at going thirds on a montereay 224fsc speedboat, 22' with cuddy. It has the mercruiser volvo 4.8 or 4.8 not sure petrol engine.

Any ideas on likely fuel consumption in a real life environment?

Been told 5 gallons an hour at speed!! but this seems a little unlikely to me.

Cheers

[VvrooomM]

uk gallons

[danyeates]

5 gallons an hour? Would have thought it would be more than that.

My RIB has a Yamaha four stroke 150hp engine (2.7 litre 4 cylinder) and that cruises as about 22 knots at around 23 litres per hour, so around 5 gallons per hour. My RIB is only 6m, just under 20' in old money.

My old RIB (5.6m) had a 115hp and used to do only 14 litres per hour at the same speed. Big jump in fuel consumption.

[danyeates]

Also, it will be either a Mercruiser or a Volvo, they're different companies, and most likely the 4.3L V6.

Found this test: http://www.boattest.com/oem/test-results.aspx?ID=9...

Suggests what I said, 20 knots about 5 gallons per hour, then goes up considerably from there. This is on an 18' 5" sportsboat just as an example.

Edited by danyeates on Sunday 3rd October 15:35

[IforB]

5 gallons an hour seems a little low to me too. I'd expect and plan for closer to 7.

[richardxjr]

Budget for an average of £1 per mile and you won't be far wrong.

[VvrooomM]

sorry i meant volvo penta or mercruiser

[VvrooomM]

4.3 volvo penta and broker suggests 4 gallon per hour at 20-25 knots which works out about £1 per mile

[Huntsman]

VvrooomM said:

4.3 volvo penta and broker suggests 4 gallon per hour at 20-25 knots which works out about £1 per mile

4.3 is V6 I think.

4 gallons an hour at 20 to 25 knots is a crap answer, at 20 knots and at 25 knots the consumption will be quite different. 25 knots is 25% more speed than 20 knots, I'd expect 25 knots to require at least 30% more fuel than 20 knots.

If you plot a graph of speed and consumption its a parabolic curve and gets very steep the faster you go.

There are no 'free' knots, the faster you go, the more it'll drink. Sea state, cleaness of the bottom, number of people on board etc all have a bearing on it.

Edited by Huntsman on Monday 11th October 22:28

[jenkotvr]

This weekend I used £30 for 2 hours pottering around through the swellies (Menai Straits) on my 15ft Fletcher (75HP Mercury)....i must say, most enjoyable.....who needs these big thirst pockets

[andy c]

This is a difficult subject....too many variables.

ie Sea state,
Speed travaling at
Fuel load,
Boat load,

A boat that if full of fuel,full of people and their gear in a sea that has tide against you etc,etc,etc you get my drift, would make the boat substantially less economical as a boat travalling light.

I have a 24ft with a Volvo V8 and a couple of beds and a bog,dinghy and 4 adults.I only ever put in 50- 80 litres at a time[biiiig mistake when I filled it up full with 300litres] and minimise the amount of gear we take.I do a regular trip of 60 miles and we use 80 litres poodling along at 20 knots, in a calmish sea with no tide.

PS. we are most economical flat out,I have a fuel consumption /MPG gauge that also tells me how many litres used and how much is left.Very acurate and Well worth it!!!.

0.7-0.8 mpg is the norm for me but we weigh probably near to 3 tons.
The V6 in a 22ft cuddy could be more a bit more economical but loaded up may end up worse.Like I said, so many variables.I would be surprised if you didnt hit 1mpg

Edited by andy c on Thursday 14th October 10:29

[Yuxi]

I think you mean 1 mile per litre

[Simpo Two]

andy c said:

PS. we are most economical flat out

For that to make sense you'd have to be planing, no?

[andy c]

Simpo Two said:

andy c said:

PS. we are most economical flat out

For that to make sense you'd have to be planing, no?

It hits about 0.85mpg on the gauge at about 6-7 knots when not planing and then again at about 28-30knots.we cruise at about 20-25knots and it goes down to about 0.75 mpg, but is more relaxed and the engine is old now so less strain on the motor.Bearing in mind we are not antifouled and no tidal streams, not much wind and the waves are normally minimal as it is in the med.When we were anti fouled it was less.In fact when we are light and flat out it will do about 35knots unantifouled, compared with about 28 when it was.

I think this gauge is pretty acurate. We run it down to almost zero litres left on the guage and have never run out yet.We do have a separate 30 litre reserve tank for emergencies or for the dinghy if needed.


PS. I will add that the system I have is Navman,and was easy to fit.
It displays:
FUEL USED-
FUEL REMAINING IN THE TANK-just add the number of litres manually into the gauge when filling up.
MPG-
MILES UNTIL YOU RUN OUT-
SPEED-
Distance travelled-

All on one gauge with multi display.I wouldnt be without it.
I calibrated fuel flow when fitted and its been very accurate since.
Peace of mind.

Edited by andy c on Saturday 16th October 12:39