chuzzlewit
Well-Known Member
Is there a simple formula to estimate this? How much more efficient is 4stroke than 2stroke?
O/B fuel consumption
- Thread starter chuzzlewit
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m1taylor
Well-Known Member
Depends very much on size of outboard - 2hp or 75hp? Also the load under which the outboard is run makes a huge difference.
VicS
Well-Known Member
Ive never seen a formula. My 6hp Evinrude 2 stroke uses about 1/2 gallon per hour at a steady plodding along sort of speed.
Reference to some old outboard tests in past issues of PBO might give you some idea of the difference between 2 and 4 strokes, but I'm not sure they ever consider fuel consumption.
Reference to some old outboard tests in past issues of PBO might give you some idea of the difference between 2 and 4 strokes, but I'm not sure they ever consider fuel consumption.
reginaldon
Well-Known Member
My oldish Yamaha 5 2stroke averaged a litre and a third per hour - again at a plodding speed over 10 hours in a calm
Drascomber
Well-Known Member
Hi Chuzzlewit.
4 strokes are generally much more economical than 2 strokes. As the emissions regs get tougher they are getting even more economical.
My 2 stroke 6hp Yamaha consumed about as much as Vic's maybe a little more say about 2.5 litres an hour at cruise.
My slightly overpropped 4 stroke 6 hp Mercury has a max rpm of 5,000. Because it was overpropped last year it would only pull 4,800 rpm which gave 6.1 knots. At around 3,800 rpm it sips about 0.9 litre. On my boat last year those revs equated to a fast cruise of around 5 Knots.
The latest model has variable ignition timing (which mine doesn't have) so should be even more economical.
I would expect big HP engines also to show big LPH improvements for the same (emissions) reasons. In fact with the sophisticated engine management you can afford to put on an engine that has to be craned onto the transom the savings should be even greater.
4 strokes are generally much more economical than 2 strokes. As the emissions regs get tougher they are getting even more economical.
My 2 stroke 6hp Yamaha consumed about as much as Vic's maybe a little more say about 2.5 litres an hour at cruise.
My slightly overpropped 4 stroke 6 hp Mercury has a max rpm of 5,000. Because it was overpropped last year it would only pull 4,800 rpm which gave 6.1 knots. At around 3,800 rpm it sips about 0.9 litre. On my boat last year those revs equated to a fast cruise of around 5 Knots.
The latest model has variable ignition timing (which mine doesn't have) so should be even more economical.
I would expect big HP engines also to show big LPH improvements for the same (emissions) reasons. In fact with the sophisticated engine management you can afford to put on an engine that has to be craned onto the transom the savings should be even greater.
roly_voya
Well-Known Member
Put it this way since I changed to a 4st I generally find I need to empty the tank before the fuel goes off
Hardley
Well-Known Member
I would say that 4 stokes are more economical.
As for liters per hour, much would depend on boat, shape, weight etc.
I have an old Yamaha 8 and at 5 knots I get 1 liter per hour, pushing it up to 6-7 knots it consumes 2 liters per hour.
I have the engine serviced every year, so that it is kept in good condition.
As for liters per hour, much would depend on boat, shape, weight etc.
I have an old Yamaha 8 and at 5 knots I get 1 liter per hour, pushing it up to 6-7 knots it consumes 2 liters per hour.
I have the engine serviced every year, so that it is kept in good condition.
reeac
Well-Known Member
[ QUOTE ]
Is there a simple formula to estimate this? How much more efficient is 4stroke than 2stroke?
[/ QUOTE ]
The old rule of thumb is 10 bhp.hours for a gallon of 2-stroke and 15 bhp.hours for a gallon of 4-stroke [the fuel, obviously, being used in the appropriate type of engine]. That means that for a given usage the 4-stroke will go 50% further per gallon.
Is there a simple formula to estimate this? How much more efficient is 4stroke than 2stroke?
[/ QUOTE ]
The old rule of thumb is 10 bhp.hours for a gallon of 2-stroke and 15 bhp.hours for a gallon of 4-stroke [the fuel, obviously, being used in the appropriate type of engine]. That means that for a given usage the 4-stroke will go 50% further per gallon.
