Diesel VS 4 stroke outboard fuel consumption

Well would someone post these gas outboard fuel curves instead of talking about them??

Can't find any fuel curves for any outboards on their factory sites or anywhere on the web except this from an Aussie site that did a good comparison betwixt 2 similar outboards:I've edited out extraneous stuff

FACTS & FIGURES on Honda BF30
Trolling at an estimated 800 revs the Honda averaged 0.5lt/h on 900 revs
4000 revs using 5.1lt/h .
(WOT) Honda and 10.3lt/h on 5900 revs At WOT

So to put in form: Honda BF30 4 stroke gas outboard,30 HP:
-??hp @ 4000 rpm @5.1 l/hr
-30 hp @ 5900 rpm @10.3 l/hr

Taking Catbuilder's kind link to a yanmar chart
http://shop.torresen.com/utility/includes/content/yanmar/sales_lit/3YM30.pdf


Approximately:

We see the yanny does not get to the honda's 4000 rpm:
-taking the Honda's 5.1 l/hr ( so 1.34 US gph) and taking it to the Yan chart it would be at ~3200 rpm on the Yan which scrolling across to the prop shaft hp dotted line= 26 horsepower or thereabouts.
-taking 10.3 l/hr from the Honda (seeing as it's rated at 30 hp) we go to the yanny's fuel curve and oooooops the yanmar's maximum consumption can't even get to 10.3 l/hr.
WOT is 1.8 gph which is =7 litres per hour.


Gas Honda BF30 outboard produces 30 hp@ 10.3 litres an hour
" " " " " and ?hp@ 5.1 litres an hour
Diesel Yanmar produces ~26 hp@ 5.1 litres an hour AND
Diesel Yanmar produces 30 hp@7 litres an hour.


Cut and paste of Yamaha:

Yamaha F30A:
-Cruising quietly at 4000rpm, 5.0lt/h and the WOT averages were 10.5lt/h on 5700rpm.


Addendum: found Nissan site:
http://www.nissanmarine.com/tech_talk/gas_mileage.html

-30hp 4 stroke 9.9 l/hr at wot
-30hp 2 stroke 13 l/hr at wot.

But outboards are not designed for WOT running,whereas the Yan will run for thousands of hours at the rated 27 hp.

 

Guess you are using the Honda engines because they are less efficient than the Yamaha?

Do you own stock in a diesel refinery or something?

 

Guess you are using the Honda engines because they are less efficient than the Yamaha?

Do you own stock in a diesel refinery or something?

 

lol no didn't notice yamaha on next page until post all done.

Once again,horses for courses but at the end of the day no matter what anyone says,diesel is more efficient.

End of story.

 

Also bear in mind that the Yanmar is not a very efficient machine because it has direct cooling and cannot reach optimal combustion temperature.
And sad, but these outboard are no longer in production.

The Nissan revelations are quite interesting and daring. We all knew outboards waste lots of fuel, but exactly how much has always been a well kept secret.

 

I would say versus a pleasure craft diesel rating the outboard IS designed for continuous WOT

 

As long as we are taking displacement boats, yes.
If planning then weight becomes an issue just like when comparing V6 4s outboards versus v6 Brp etecs. Etecs are lighter so they go generally go faster so when backed off can equal a 4s outboard at the same speed.

 

Actually, I agree. In currently popular choices for propulsion, diesels are more efficient. That efficiency difference is 7%.

Operating cost in the states is 1 cent more efficient per hour.

 

"I would agree that absolutely no inboard gas/petrol engine could ever touch an inboard diesel for efficiency."


Would be nice if this were true, But , the drop off in the diesel efficiency is far more than the gas efficiency at partial throttle.

You might be be correct with a boat requiring say 30 hp, with a diesel that ran (say 80% Rated load -90% rated RPM) at 30 hp all the time.

No reserve for a HEADWIND OR SEA STATE.

A gas engine will frequently be efficient enough at its torque peak (modest RPM) that IF it produces similar 30hp at that RPM the fuel burn may be even lower than the diesel..

Simply put diesels loose fuel efficiency BIG TIME at partial throttle , gas far less.

Diesels love close to 100% throttle , gas is great at 50% rated output.

Efficiency also should be figured on lifetime costs , maint and fluids , PM and rebuild costs.

Diesel lube oil, antifreeze, and required procedures for "out of service over 30 days" , are quite high . compared to most gas engines.

Total expense per year or decade is far more Efficient to monitor than mere fuel cost per hour.

FF

 

That, of course, is one of these unique FF statements.

Attached is the performance graph of a randomly picked modern marine diesel, a 164 hp 4-cylinder Steyr.

At full load and rpm, it consumes 250 grams of fuel for every kW. Any setting below 4000 rpm shows reduced consumption, down to 210 gr. between 2000 and 2800 rpm.
Maximum consumption for this engine is 30 kg per hour, or 43 ltr, or 11,3 gallon.

This sort of data is hard to find for gasoline engines, but WestVanHan found a really candid site with full throttle consumption figures for all Nissan outboards, both 2 and 4 strokes.
Look at the NSD115, a state of art engine using direct fuel injection to improve "efficiency". It consumes 12 gallons, but produces only 115 hp.

That is 30% less power for the same amount of fuel!

It is very hard to find arguments in favor of outboards. They are thirsty, noisy, short living and are prone to theft.

But I do envy my neighbor's shiny stainless prop, lifted clear from the water.....

 

Cdk: I only see 3 real arguments for outboards. I agree they are few.

1) I'm a sailboat guy. My boat sails significantly faster when I don't drag a bunch of junk through the water. Outboards provide 0 drag if sailing.

2) If they invent a new power source or you need to fix by a service shop, you can remove and replace in minutes.

3) Lower initial cost.

4) No through hulls and no need to have zinc anodes. No metal below the waterline.

 

Cdk: I only see 3 real arguments for outboards. I agree they are few.

1) I'm a sailboat guy. My boat sails significantly faster when I don't drag a bunch of junk through the water. Outboards provide 0 drag if sailing.

2) If they invent a new power source or you need to fix by a service shop, you can remove and replace in minutes.

3) Lower initial cost.

4) No through hulls and no need to have zinc anodes. No metal below the waterline.

 

On a displacement boat yes, on a planning hull the arguments can be either way

 

I agree with ~30%, minus a little for extra weight. I haven't had an outboard stolen, but then I take it (30HP) off and take it home.

 

Outboards are wonderful!
With that said I'll try to say something objective.
Where is this debate at this point?
Are we debating specific propulsion systems on specific boats?
Or are we debating the efficiency of engines of about the same size and made for the same purpose? You can compare the OB to the inboard only if your'e comparing "systems" not "engines". The small 4-stroke OB like a 15hp Yamadog is optimized as a "kicker" on 20 to 28' planing hulls like charter fishing boats here in Alaska to troll-fish. Some people would say most or many of these engines were used as sailboat engines. Probably sailboaters.I think not. But my point is that you see lots of them on both and the job to be done on each is much more different than gas v/s diesel. If a 15hp OB is optimized to push a 25' planing hull at trolling speeds it will almost always be way way off for sailboat power. On the other hand the diesel in the sailboat will probably be close to optimal.
So where does this debate, conversation or discussion stand?

Easy Rider