Fuel consumption figures?

[cliffdale]

Can anyone show me a site where I can get fuel consumptions for the following engines.

All Volvo
KAD32
KAD44
KAD300
D4/ 260s

Im changing boats but would like info on fuel and efficiency of the engines.

I looked on Volvo Penta site but could not find information on the engines.

Im forward planning for the dreaded decision in 2006, which seems awfully close now!

 

[DazedConfused]

You will probably have to checkout the boat manufacturers as each engine can be installed into many type of boats which would lead to large differences in fuel consumption ie. hull shape, boat weight, single/twin engine, etc.

 

[Gludy]

As stated already the fuel consumption figures vary a great deal not only with the hull type but with the speed.

For example, if you chose a semi-displacement hull type fuel consumption figures at the lower speeds may be a fraction, say 20% of the figures at higher speeds.

On the other hand if you choose a planing hull, you really do not have this choice and also normally have a very flay fuel consumption over the planing speed.

So if you wish to really take 2006 into account, the question of what hull type to go for should be asked.

One example of the difference is:-

Planing hull boat at typical cruising speed of 25 knots say 100 units of fuel.

Semi-Displacment hull at 10 knots 30 units of fuel, at 18 knots 100 units of fuel, at 25 knots 150 units of fuel.

So with the SD hull you at least have the option at going at different cruising speeds and so if red went to road levels would have the option of of having the same fuel bill at lower speeds.

Of course this is not the only factor for the SD hull, the biggest is the smooth ride - with the ability to walk around the boat etc whilst underway intead of just holding on as it were.

So, if you wish to be as immune as possible to the red question, the SD hull should be considered.

 

[oldgit]

Whatever happens re fuel.Think that consumption will appear higher and higher on the list of need to think about stuff.

 

[Gludy]

Spot on .. we agree Oldgit!!! No matter what happens to red fuel consumption will appear higher and higher on the priority list.

If this is accepted then it adds more weight to the boat with displacment or semi-displacment hulls.

I personally give a lot of weight to enjoying getting there as well as being there. Even on a 60 foot planing hull passengers are simply holding on whilst crusing in almost any sea state. A trip to the heads has to be handled with care. Hence an SD hull, with stabilisers, offering a very good ride that allows passengers to use the boat when in passage, is a huge factor for me. As a bonus it offers a choice of speed/fuel consumption and a much safer hull (Class A) with the ability to dry out and so open up many more harbours. The sacrifice for this is to drop the cruising speed 8 knots in calm conditions. In rougher conditions it has the ability to maintain a higher speed than the planing hull. Also there is some loss in the medallion man type of image...... I can live with these sacrifices

If all I was using the boat for was to pop out of harbour, visit a local bay and back then I can see some attraction to the planing hull .. and I can see its use doing that in the Med .... but for any serious cruising the SD hull for me wins hands down.

 

[pissativlypossed]

If you search the Volvo web page they give fuel consumption figures in litres per hour across the rpm range

 

[Roy]

A forumite on here posted last year that a gallon of diesel burnt will produce a nominal 20hp - or for every 20hp expended, burn 1 gall diesel. Now I don't know whether that is correct but it seems a fair yardstick to me but would be dependent to some extent upon the resistance to the boat - i.e. loading, wind, tide, current which would have a beneficial or adverse effect? Perhaps Gludy who is very informed on this topic would add to this or nullify it? Gludy, I mean this and am not having a pop at you due to some of the longish fuel debates we have had on here. Roy

 

[Gludy]

The yardstick of so much fuel burnt for so much power output is a reasonable yardstick ... So stating that for engine XX you get yy hp from a gallon of fuel is a reasonable approximation.

However it is only part of the story.

The other part of the story is what you can do with that yy of Horse Power.
That really does come down to hull shape and the speed you travel at.
Its best to avoid speaking in gallons per hour and speak in gallons per mile as it is this that measure fuel consumption for any particular trip.

Now in terms of miles travelled that yy hp is pretty fixed for a planing vessel as these have a flat fuel consumption curve once past planing speed and are not really good sea boats below planing speed. .... its is also fixed dor a displacement hull form as these really do have an effective maximum speed but would probably get about 5 to 8 times the mph of the planing boat albeit at a much lower speed.

The semi-displacement boat would offer a choice - my next boat will be an SD hull because of the reason I have already outlined in my previous post.

What I am really saying here is that whilst the yarstick you mentioned is a reasonable yardstick to take, the original question and the yardstick really do not deal with the question of fuel efficiency ... the hull shape and the speed are the critical factors that dwarf all other differences. Any differences between one engine and another in fuel efficiency is as nothing compared to these two factors.

 

[Roy]

Cheers Paul and thanks for refining the rule of thumb.It adds some meat to the variables.

 

[cliffdale]

I take the point about the hull type and the speed you travel at.

The next boat is going to be one of these, Fairline Targa 34 or Sealine 34. I still haven't made up my mind yet, as some of you formites know!!

If we are talking of cruising speeds on a planing hull, may be someone could come up with a more accurate estimate of consumption.

The 1gallon per 20 horses is a starting point. Im under the impression that if I went for a KAD300 or D4/260, they will not be working as hard and you would throttle back and not use as much fuel?? My current 170hps tend to be open to nearly full throttle to maintain a cruising speed of 22/23 knots.

How much of a difference will I notice in consumption if I went for the bigger engine options for the 34' planing boats??

would it be worth paying much more for the bigger engine options?

Ive still not found the figures on Volvo Penta site.... Will someone point me in the right direction for revs/litres per hr.

Thanks

Cliff

 

[Roy]

Cliff.... suggest you contact Julie (Powerskipper) as she has an s34 in her family and is well experienced to answer this.

 

[Gludy]

"If we are talking of cruising speeds on a planing hull, may be someone could come up with a more accurate estimate of consumption."

The fuel consumprion on a planing hull is normally very much the same once you are over the hump and planing. That us until you squeeze the last few knots out when it will suddenly rise again. Typically a boat doing say 24 to 26 knots cruising wil a top of say 31 knots will have almost the same mpg from 16 kots through to 26 knots. ... it s very flat relationship.

I know some who cruise in such boats at 20knots to save fule but I think they are deluding themselves. Once such a hull is planing the more poer you apply the faster you go and the extra distance covered at the higher speed equates to the fuel being used at the higher power level.

The differences in the hull shapes between two planing boats are going to matter more than the differences in make of engines. So you are searching for figures which are not significant when the real significant thing is the difference in the boats.

As regards engine size I have Fairline Squadron 59 with twin 600 hp engines that are very easy to get at and maintain. It wants to cruise at 26 knots all day and has a top of almost 31 knots. I cruise at 200 rpm below max rpm. The same boat fitted with heavier 700 hp engines (leaving no proper room and maintainance headaches) has the same top speed and about the same crusing speed, so from my experience to date I would go for the smaller lighter engine as long as that at its all day happy rpm is giving you the cruising speed you require.

The only way to get this info is, has as already been suggested, from other userss of the boats you are looking at. even then, few will actually know their real fuel consumption!