Question about fuel consumption for you motor boaters from a yotty

[Sticky Fingers]

Ha yes wrong way round!

 

[Irish Rover]

My 43' powercat has 2 Yanmar 320hp engines. In a calm sea max speed is 24/25kts burning around 65L per engine per hour. Making 20kts they burn around 110L combined so 5.5L per NM. I'm rarely in a hurry and almost all of my motoring is at a leisurely 7 - 7.5 kts burning on average a combined 9lph (4.5 ×2) or 1.25 litres per NM. Diesel here in Türkiye is less than a pund per litre. What's not to like.

 

[oldgit]

ACM 38 with a pair of 4 cylinder 240HP Yanmars.
About 120 hours this year .
Frequent local days out usually with a short whizz at the end plus few weekend trips to nearbye non tidal waters usually at 6-8 knots displacement.
More extended Jaunts of a week or so to upper Thames,central London marinas and channel ports at both displacement and frequently unplanned hurry up whizzes when either boredom or weather intervenes.
One trip across the channel with a return at more or less WOT simply get get out of it and home.
Home Fuel @ £1.00 per litre. Worst 1.76 Euros.

 

[Sticky Fingers]

So, what was your average consumption?

 

[oldgit]

Calculations brim to brim according to log book.

July 24 to July 25.
154 hours.
2859 Litres
Consumption both engines. approx 18.5 litres per hour in total.
Litres per mile seems pointless to me, its how long before your engines stop.

The things that break/ drop off/ need replacing .....works out at about 1 per 10 hours run over the same period .
Seem to have misplaced anything that reminds of booze, food or marina bills.

 

[Alicatt]

Calculations brim to brim according to log book.

July 24 to July 25.
154 hours.
2859 Litres
Consumption both engines. approx 18.5 litres per hour in total.
Litres per mile seems pointless to me, its how long before your engines stop.

The things that break/ drop off/ need replacing .....works out at about 1 per 10 hours run over the same period .
Seem to have misplaced anything that reminds of booze, food or marina bills.

Ours is coming due, also the year's electric bill
Done around 760km on the canals this past year, put 618 litres of diesel in at the start and the tanks are still more than half full, maybe 2/3full, tanks hold around 900 litres, we will see when we go to fill up.
The only fuel curve I have for the boat starts at a higher RPM than we cruise at, fuel curve starts at 1000rpm and most of the time we are 700 to 900rpm, anyway the curve says 2.7litres per hour per engine @1000rpm at 1000rpm we are doing around 7knots

 

[oldgit]

Helped to bring back a few boats from south coast , Corniche 31 , P35 and a F44 all required a mid trip top up in Ramsgate, the ACM came straight past on its way back to the Mudway.
Two out of the three broke down,
That F££ drinks like fish
Greenline 39 with single D3 moved to the Thames did it apparently without the fuel gauge actually moving

 

[MapisM]

Litres per mile seems pointless to me, its how long before your engines stop.

Why on earth do you care about that? It's how far before your engines stop that really matters, rather than how long!
Of course you can also calculate that starting frm lph, but by using lpm you just skip one useless calculation step.

 

[oldgit]

Why on earth do you care about that? It's how far before your engines stop that really matters, rather than how long!

With MPL .
Assume 10 miles per litre. ? We wish
Going with a 3 knot tide a litre will get you 12 miles.
Punching a 3 knot tide your litre will get you 8 miles.
Four miles difference.
With LPH you know how long before your engines conk out irrespective of tidal direction or strength.
Six hours against a 5 knot tide can considerably affect your distance over the ground ?

 

[MapisM]

Six hours against a 5 knot tide can considerably affect your distance over the ground ?

Absolutely.
But if your engine instruments provide the fuel burn in real time, as most electronic engines do, it's easy to interface that to the GPS, getting the actual SOG-based fuel burn at any given time.
Which keeps into account not only tide, but also the boat load and possibly fouled hull/props.
Besides, with some instruments you can also key in the tank capacity and the refill quantities.
This way, on top of the numbers that you prefer (liters or gallons, per hour or per mile, whatever) you can get directly the residual range, in real time and depending on current cruising conditions.

Now, I'm well aware that not all boats are equipped with all these bells and whistles - also mine isn't!
But when you don't have reliable fuel burn instruments, the preference for one or the other type of calculation becomes a bit academic.
In fact, nowadays I can't be bothered to do any math: I just check now and then my tank level with the most accurate and reliable system known to mankind (sight gauges! ), and when the level is worryingly low, I go for a refill - job done.
I did take notes on fuel burned, running hours and miles right after I bought my boat, which back then was completely new to me.
But since I never make passages anywhere near her max range anyhow, it's a habit that I lost PDQ.
Life's too short!

 

[Fire99]

This may be unpopular to some but I try not to calculate the figures too closely as they'll probably scare me a times. I've worked out the general fuel cost for trips, I.e., Near 2 weeks going port to port in the Western Isles of Scotland has worked out around £900-£1300 depending on route and distance. I use my digital displays to find a balance between making decent progress and not rocketing the fuel use.. Then I approx. budget the trip rather than the lph or mpg. There may be a little burying my head in the sand, but it works for me.

Funnily enough my previous boat was a sailing boat that I tried to sail on and off its swing mooring. The fuel was (maybe) more likely to go off than be used up A different world of boating.

 

[Assassin]

Bottom line is simple, if you can afford the boat you can afford the fuel, if you cannot afford the fuel you cannot afford the boat.

 

[ari]

Some truth in that. I use my boat quite a bit and keep accurate tabs on all costs. Fuel works out at less than 10% of total expenditure every year.

That said, I probably wouldn't want to run a petrol boat, so the fuel cost is far from irrelevant.

 

[Irish Rover]

Bottom line is simple, if you can afford the boat you can afford the fuel, if you cannot afford the fuel you cannot afford the boat.

That might not be everybody's bottom line. I can afford the fuel for my boat whether I'm burning 65 LPH or 5 LPH. Which do I prefer? Guess! At 7kts I can relax and enjoy the ride. I'm doing it for enjoyment. If I don't get there today, I'll get there tomorrow. Still, it's nice to know I have 640 horses under the bunks when I need to move a bit faster. Same goes for my EV. I drive it in Eco or Normal mode, never in Sport mode, even though I charge it at home off the solar panels on my roof.

 

[Wasp]

for a 52 foot boat seems about right my 58 is between 8 and 10 depending when I last got it cleaned and the sea state.

Forgot to mention that, becuase she was lifted and scrubbed for the survey, the hull is as clean as it can be. I know from experience that this makes quite a difference.

 

[Alicatt]

Ours is coming due, also the year's electric bill

Electric bill for the year was €170 and for 3 months covered 2 boats.