Rule of thumb for motoring range

[DaveNTL]

Of course there are countless variables, but does anyone have a rule of thumb or a link to a table where you can estimate a boats range given a few parameters such as LOA, displacement, engine type / size and fuel tank size?

 

[Shantyman]

There are some good on-line calculators on boatdiesel.com
This is an American diesel engine forum so the answers are in U.S Gallons and the calculators are available to members only.

PM me if you have any problems.

Shantyman.

 

[VicMallows]

Unfortunately, your profile gives no indication of the sort of boat you're talking about. Otherwise, we might be able to help.

Vic

 

[DaveNTL]

I was wondering what sort range or motoring hours a Nauticat 38 would have - it has a 150 gallon tank and a 110HP engine.

I'm familiar with Island Packets and know the ranges of motoring hours for a particular model / engine combination. Being a motor sailor the Nauticats engine has twice the horse power of an equivalent sized IP and 75% more fuel storage, so I was wondering how it's range would compare.

Then I looked around for some rules of thumb, but a forum and Google search didn't help.

Dave

 

[zefender]

This webpage gives some info on range for a 110hp Nauticat 38 of 1111km on a 620l tank

 

[DaveNTL]

Thanks for that zefender, Vic and Shantyman too.

 

[nealeb]

Not sure about the other vendors but Yanmar appear to publish engine speed/fuel consumption curves (see specification sheets for individual engines). If you know revs for a specific cruising speed for your boat (and assuming that the prop is correctly matched to the engine) you could get the fuel consumption from that. If you are really keen and check revs vs speed over a range, you could even calculate optimum cruising speed for max range. Does depend on your engine manufacturer publishing the fuel consumption curve, though!

If you really want an estimate for an unknown boat, I would start with maybe 80% max revs and use hull speed (1.3*sqrt(LWL), etc). For my boat, that gives 2800rpm, consumption 0.8gal/hr, hull speed 6.9kts, and around 8.6nm per gallon. In practice I tend to cruise a little more slowly (and underload the engine...) but probably get somewhat better fuel consumption. Given that I didn't even put fuel in my 35gal tank last year, it's not something that worries me too much!

 

[philmarks]

I have a 130hp Mercedes, 38' W/L, fin keel and use 1 litre per nautical mile at 6kts/2000 rpm in average conditions. That's the economy setting! If it's choppy then she'll run at 6kts stw, flat calm 7 kts stw at those settings.

For my interest only, with a 150 gal tank, 660 litres, I'd estimate you have 800-900 miles range at cruising speed (working on 3/4 litre per mile for 110hp engine in average conditions). But of course you don't want to run your tank down to empty...

Any other offers out there?

 

[Guest]

Mmmmmmmm - tried a table ....

Range is actually not a valid argument .... too many variables affecting it and best is time duration per tank.

Most people will know their boats speed and tank size .... once you have consumption - time possible on a tank is easier to gauge. I know that the question is likely prompted by a wish to work out if a run across xx is possible on a tank etc. - but change tide / weather / wind etc. and one day yes - another no .... but engine run time will be similar ....

 

[DaveNTL]

good info phil, thanks

i agree nigel, thats what i was saying in my original thread, too many variables to be acurate but of course when comparing a boat type you know to one you don't it's good to have a good feeling for what your 'range' is and I didn't know where to find it - the forum came up trumps

anyway chaps and chapesses, I got the contract back for the Nauticat today! weyhey! *cracks second bottle open* cheers!

 

[Anonymous]

Enjoy the Nauticat! We have been proud Nauticat owners for just 5 months (living aboard) and haven't regretted the decision once.

David