fuel consumption

[scoty]

NISSAN A4.28 engine . two of them fitted in a displacement nine meter motor boat, anyone out there know what the fuel consumption could be at 1800rpm, also I·m advised not to put an anti-bug additive in the fuel for this engine,,,,,any comments much appreciated.

 

[Divemaster1]

All a question of how much load is in the engines (hp taken out) .... and the conditions & configuration of the boat at the time...

If you can tell us the ratings of the engines, max RPM (and if you achieve this), combined with your waterline lenght of your vessel and the speed you achieve at 1800 RPM, we could make an educated guess of an approximation... all which would wary with sea conditions etc..

 

[scoty]

Thought it was more to do with ,,,two 82HP engines working together in a nine meter displacement boat at 1800rpm ,,,flat sea, new antifouling,,,,

 

[Divemaster1]

No ... it does not ... enjoyable as that may be .... , fuel consumption is about how much you take out of those engines (propellor load) at the given RPM ...

If you take out 50% of the engines (that is not 50% of RPM), you will burn approx:

82 Hp @ 200 - 220 gramme per HP/hr (pretty std guess on energy of marine diesel)

1 Litre of Marine Gas Oil (MGO) weigh approximately 0.86 Kg, which means 0.232L per hp/hr (@200g/hp/hr) x 82 = 19.1 L per hour....

So if your engine load is higher at the given RPM, then consumption will differ....

 

[mikesyam]

Alf I so love your replies.

Mike

 

[Divemaster1]

Alf I so love your replies.

Mike

Too factual perhaps ??

Very few UK leisure boats cruise for many hours at a given speed for more than a couple of hours ... as such the figures will inevitably be changeable... never mind the conditions affecting the consumption....

My replies should get better the more local produce is consumed ... found a great little place today ... GlenDronach ... and working my way through 12, 15 & 18 ...

Need to head for the boat soon ... but got enjoyably delayed when I found the place above..

 

[scoty]

but not much help in answering the basic questionS,,,so anyone with more, or less practical experience feel like replying ?

 

[cryan]

I would guess at between 1-3 litres per hour each. But thats just a guess as fuel consumption can be different on two identical boats fitted out the same. It depends on hull cleanliness, prop condition, bearing condition, engine condition, exhaust condition, sea state, tidal state, sea temperature, air temperature, fuel condition etc etc. The only way you'll really know is to take calibrated readings of the fuel you actually use and start a graph so you will have an idea for future reference.

 

[FishyInverness]

RNLI's website has a very simplistic view:

Diesel
• A diesel engine burns about 1 gallon per hour for every 20hp. So a 90hp diesel would use about 90/20 = 4.5 gallons of fuel per hour. For those who prefer to work in litres then simply multiply the horsepower by 2 and then divide by 9. So a 90hp has an estimated consumption of 2 x 90/9 = 20l/hour.

 

[Elessar]

I would guess at between 1-3 litres per hour each. But thats just a guess as fuel consumption can be different on two identical boats fitted out the same. It depends on hull cleanliness, prop condition, bearing condition, engine condition, exhaust condition, sea state, tidal state, sea temperature, air temperature, fuel condition etc etc. The only way you'll really know is to take calibrated readings of the fuel you actually use and start a graph so you will have an idea for future reference.

so assuming 6 knots, about 4.5-13.5mpg. if it was 8 knots 6-18mpg. I don't think so!

 

[rustybarge]

Perkins 84 hp is similar:

Specifications - M92B
Description Specifications Performance Equipment Installation Drawings


Engine Configuration: 4 cylinder, in-line vertical, 4 stroke, water cooled
Aspiration: Naturally aspirated
Bore / Stroke: 105 mm (4.13 in) x 127 mm (5.00 in)
Displacement: 4.4 litre (269 cu.in.)
Combustion system: Direct injection
Compression ratio: 18.23:1
Engine Rotation: Anti-clockwise viewed from rear.
Fuel Injection Equipment: Delphi rotary with electric stop.
Continuous Engine Operating Angles: 20 ° front up
25 ° sideways (35° sideways intermittent)
Power Take Off Available from front end drive (for drive limitations refer to Sabre Engines Ltd).
Weight (Wet):
423 kg (933 lb) engine only
460 kg (1014 lb) with ZF 45A reverse gearbox
504 kg (1111 lb) with Newage PRM500D reverse gearbox

View attachment 34433


So at continuous cruise of 2200 revs....15 ltr per engine.
Or at 1800 revs .....7 ltr/hr

 

[scoty]

many thanks,,,most helpfull