Update & Corrected Running Costs

[Mindi]

The intention was and still is to highlight the growing impact of fuel costs on our motor choices. It's not about bagging Etecs or 4 strokes...its about understanding the costs. The idea was OK I thought except I made a mess of the numbers. I cant attach an Excel spreadsheet to a thread here so the numbers are...

Running Costs over three years

If you do 50 hours/year

Suzuki 70/90........$3900
Etec 75.................$4311 ( +411)
Opti 75.................$5568 ( +1688)

If you do 100 hours/year

Suzuki 70/90........$6705
Etec 75.................$8172 ( + 1467)
Opti 75.................$9429 ( + 2724)

Happy to PM anyone who wants the spreadsheet. Of course this is only one factor in choosing a motor and does not take into account performance, original cost or resale value, or reliability...just week to week running costs

[two up]

Mindi,
great idea, how do you arrive at these figures. Is it simply the price of gas to run 50 and 100 hours and ( oil for 2 strokes ) service costs or is there something else in your calculations.

[Mindi]

Mindi,
great idea, how do you arrive at these figures. Is it simply the price of gas to run 50 and 100 hours and ( oil for 2 strokes ) service costs or is there something else in your calculations.

fuel, oil and service only. Based on 11.0 lph for a suzi 70 at 3500 and 14.2 lph for a Etec 75 at 3500 rpm, XD100 at $11.50 litre, fuel at $1.70 litre, and services as advised by three dealers. Consumption figures from manufacturers websites.

[Jabba_]

Mindi,,, are you still basing your fuel figures on liters per hour?.... If so, the out come is still going to be inaccurate.... You need to define an actual average distant traveled per year, and then calculated speed, distance and time travelled.... Example... I 80% off the time travel at 3200rpm @ 34mph @ 30ltr/hr, so it would take 2.9hr to travel 100mile and 87liters....

Say in with a differant motor (same boat) @ 3200rpm will do 25mph use 25lt and it will take 4 hrs to cover 100mile, and at that it will consume 100ltrs......

So you cant just base your maths on liter/hr... You need to define there cruise speed and at what rpm, and then there liter/hour

[uripper]

Mindi

Great topic - one Ive been contemplating for a while - as an owner of a late model 130hp 2stroke, none of the primitive number crunching I've done comes close to warranting a change over even at $2.00/litre - thanks for objectivity - will PM you for spreadsheet details

Mal

[Mindi]

Mindi,,, are you still basing your fuel figures on liters per hour?.... If so, the out come is still going to be inaccurate.... You need to define an actual average distant traveled per year, and then calculated speed, distance and time travelled.... Example... I 80% off the time travel at 3200rpm @ 34mph @ 30ltr/hr, so it would take 2.9hr to travel 100mile and 87liters....

Say in with a differant motor (same boat) @ 3200rpm will do 25mph use 25lt and it will take 4 hrs to cover 100mile, and at that it will consume 100ltrs......

So you cant just base your maths on liter/hr... You need to define there cruise speed and at what rpm, and then there liter/hour

Jabba
Not convinced by your argument for two reasons..

1. The whole thing is comparative rather than absolute...and the comparison will be accurate enough even if the 11 is really 9 and the 14 is really 12..?? The point is to see how a 4 stroke compares with a DI 2 stroke...


2. In any case litres/hour is (IMHO) more meaningful... as distance travelled over the ground is influenced by external issues like tide, current, weather etc etc ...running hours of the engine at a standard rpm is just that...running hours at a standard rpm...how far you go is not a relevant parameter....otherwise benchtests would be meaningless..?

[Outsider1]

Jabba
Not convinced by your argument for two reasons..

1. The whole thing is comparative rather than absolute...and the comparison will be accurate enough even if the 11 is really 9 and the 14 is really 12..?? The point is to see how a 4 stroke compares with a DI 2 stroke...


2. In any case litres/hour is (IMHO) more meaningful... as distance travelled over the ground is influenced by external issues like tide, current, weather etc etc ...running hours of the engine at a standard rpm is just that...running hours at a standard rpm...how far you go is not a relevant parameter....otherwise benchtests would be meaningless..?

I would have to disagree with you there Mindi.

Fuel consumption at a particular rpm level is not indicative of overall consumption, even on a relative basis.

I was reading Saltwater Fishing earlier and came across a response to a letter by their boating editor Andrew Norton to a question about best motor choice for a particular boat. Now in this case the motor in question was an E-Tec but could have been a number of brands. His comment was that the E-Tec would use much less fuel (than a 4 stroke) whilst trolling (over 50% less), but could use up to 15 to 20% more at cruise. Now there is one thing you can say about Andrew and that is he knows his fuel consumption info backward. I have copied the letter below so you can read it first hand.

I see lot of litres per hour fuel consumption figures quoted here and elsewhere that just do not gel. After thinking about it I have come to the conclusion that a lot of people are measuring overall fuel used against motor hours, not cruise speed usage. Why?, well most do not actually have the measuring devices and gauges to quote accurate cruise speed usage, so the only measure they have is how much fuel did I use, and how many hours did I run the motor for.

I kept accurate and detailed logs of fuel info on my old Johnson 150hp for years and it averaged out at about 12 litres per motor hour. Yet I know that at cruise it was more likely using 30 litres an hour!

Have you ever wondered why when you go on a long trip and travel at 100 or 110 kmh, that your average speed is only 80kmh?

I was watching a Top Gear clip earlier where they tested a Toyota Prius against a BMW M3 around a race track. The Prius was driven as fast as it could go and the M3 just shadowed it. The result; the Pruis used 17mpg and the M3 19mpg!

Not trying to be negative and I think the exercise you are attempting is very worthy, but I think that total fuel usage figures are a bit more complex than you have allowed.

Cheers

Dave

[Mindi]

I would have to disagree with you there Mindi.

Fuel consumption at a particular rpm level is not indicative of overall consumption, even on a relative basis.

I was reading Saltwater Fishing earlier and came across a response to a letter by their boating editor Andrew Norton to a question about best motor choice for a particular boat. Now in this case the motor in question was an E-Tec but could have been a number of brands. His comment was that the E-Tec would use much less fuel (than a 4 stroke) whilst trolling (over 50% less), but could use up to 15 to 20% more at cruise. Now there is one thing you can say about Andrew and that is he knows his fuel consumption info backward. I have copied the letter below so you can read it first hand.

I see lot of litres per hour fuel consumption figures quoted here and elsewhere that just do not gel. After thinking about it I have come to the conclusion that a lot of people are measuring overall fuel used against motor hours, not cruise speed usage. Why?, well most do not actually have the measuring devices and gauges to quote accurate cruise speed usage, so the only measure they have is how much fuel did I use, and how many hours did I run the motor for.

I kept accurate and detailed logs of fuel info on my old Johnson 150hp for years and it averaged out at about 12 litres per motor hour. Yet I know that at cruise it was more likely using 30 litres an hour!

Have you ever wondered why when you go on a long trip and travel at 100 or 110 kmh, that your average speed is only 80kmh?

I was watching a Top Gear clip earlier where they tested a Toyota Prius against a BMW M3 around a race track. The Prius was driven as fast as it could go and the M3 just shadowed it. The result; the Pruis used 17mpg and the M3 19mpg!

Not trying to be negative and I think the exercise you are attempting is very worthy, but I think that total fuel usage figures are a bit more complex than you have allowed.

Cheers

Dave

Good argument...you are basically saying that 3500rpm comparison is not able to be generalised up and down.........you may well be correct. I am assuming that the 3500 rpm figures are representative across the range. I must have another look at the original data to see what they look like at lower and higher revs. I must admit i find it hard to imagine why a DI motor would use less at trolling speeds than a 4 stroke..?
Nonetheless I was trying to give some dimension to the margin by which a 4 stroke might use less fuel. Certainly it is more complex, no dispute there, but distance over the ground is not useful because of external factors.
What you really need is (as you suggest) to be able to look at a whole of life log and say "I did 560 mixed engine hours and I used 5400 litres "

[Jabba_]

I'm not sure were you fish mindi, but in North QLD and most outside fisherman will compare fuel consumption by distance travelled / litre...
When I was at Mackey last year for the best fishing I had to head out past St Bee's and Keswick Is. That is a 25mile run by itself, so an ecomocal per hour motor is usless if it has a slow cruise speed, as it takes longer to get to the destination, so therefore it will use more fuel ... And in conversation we always talk about litres/distance,, litres/klm, and we only every use litres/hr to calculate litres/klm...
It might pay to start a poll and ask which is more relevant, liters/hour or litres/klm.......

[Mindi]

Good argument...you are basically saying that 3500rpm comparison is not able to be generalised up and down.........you may well be correct. I am assuming that the 3500 rpm figures are representative across the range. I must have another look at the original data to see what they look like at lower and higher revs. I must admit i find it hard to imagine why a DI motor would use less at trolling speeds than a 4 stroke..?
Nonetheless I was trying to give some dimension to the margin by which a 4 stroke might use less fuel. Certainly it is more complex, no dispute there, but distance over the ground is not useful because of external factors.
What you really need is (as you suggest) to be able to look at a whole of life log and say "I did 560 mixed engine hours and I used 5400 litres "

Dave

Lucky I got new glasses last week I was just able to read the letter you posted....it is very interesting and certainly supports your point...(and also supports my figures of plus 20% at 3500rpm)... well worth posting in full in somemore easily readable format.

Cheers....John

[Outsider1]

Good argument...you are basically saying that 3500rpm comparison is not able to be generalised up and down.........you may well be correct. I am assuming that the 3500 rpm figures are representative across the range. I must have another look at the original data to see what they look like at lower and higher revs. I must admit i find it hard to imagine why a DI motor would use less at trolling speeds than a 4 stroke..?
Nonetheless I was trying to give some dimension to the margin by which a 4 stroke might use less fuel. Certainly it is more complex, no dispute there, but distance over the ground is not useful because of external factors.
What you really need is (as you suggest) to be able to look at a whole of life log and say "I did 560 mixed engine hours and I used 5400 litres "

Yes,

at the end of the day it is how much fuel you have to put into the boat that really matters in a running cost comparison. So we need a measure or calculation that is the best approximation of total fuel used. Not sure on that one, I will have to give it some more thought?.

Cheers

Dave

[Jabba_]

Mindi, don't get the wrong idea that I am trying to justify any motor or what ever... just want to get a more acurite picture

I do like what you are doing..

Cheers

[Outsider1]

Dave

Lucky I got new glasses last week I was just able to read the letter you posted....it is very interesting and certainly supports your point...(and also supports my figures of plus 20% at 3500rpm)... well worth posting in full in somemore easily readable format.

Cheers....John

Hi John,

yes it got shrunk in the upload because the length exceeded 600 pixels. I have rescanned it into 2 parts and re-posted in my original thread and also here. A bit easier to read now!

Cheers

Dave

[marco]

just a small point about the cost of the xd100 . $11.50 is pretty cheap and i would like to know where i could get it for that , $14.21 per litre is what my local guy charges when buying a drum of it .

[Jabba_]

Your dealer is not doing you any favors, My dealer sells me the small bottle for $55 and a drum for $230... But having good friends in the industrie, I can get cheaper then that again...