| T O P I C R E V I E W |
| knotheadcharters |
Posted - Apr 24 2012 : 19:56:51
I know that every boat is different and there are a thousand variables but something of a base line would be a start. The boat is a 48 Californian MY weighing in at about 45k pounds. I recently purchased the boat and I topped off the saddle tanks ran approx 180 miles, mostly at 8-10 kts but did crank it up every few hours to blow out the turbos. I just refilled thetanks and by my calculations I am getting abot 3 mpg, which if right I am overjoyed but I think that is a little high. Thanks for any responses. |
| 17 L A T E S T R E P L I E S (Newest First) |
| Thudpucker |
Posted - Apr 25 2012 : 12:34:11
Guys I didn't mean to cause a ruckus.
This was "Hanger talk" I got from the Fishing industry in Ketchikan AK.
Most of those are older diesels, but I don't know the makes.
I sold my little Isuzu Diesels for a song to a guy with two boats. He liked the low fuel rate compared to a gas engine boat. |
| abalmuth |
Posted - Apr 25 2012 : 12:28:42
quote:
Originally posted by boatbum
I put diesel in, I start it, it goes. It's expensive.
Sounds just like our boat |
| boatbum |
Posted - Apr 25 2012 : 12:14:16
We have Covington 6-71TIs with N-90 injectors. Our horsepower is reported as anywhere from 340 to 410 per engine. I think we run around 7.5k at about 1000 rpm. 43 Hatteras M/Y
I put diesel in, I start it, it goes. It's expensive. |
| The Other Gary |
Posted - Apr 25 2012 : 11:16:02
My 3988 with twin Cummins 330's gets 7.8 knots at 1000 rpm
fuel burn tables show 1.55 gal per hour each at that rate for just over 2 nmpg.
My results are pretty spot on for a long cruise with a higher throttle warm up at
the start and a higher throttle cleanup at the end of each jaunt.
|
| PascalG |
Posted - Apr 25 2012 : 09:21:09
Never mind... Note to self: do not attempt basic math before first cup of coffee!!!
The DD fuel burn curves should be avail on the web, either on the DD site or on that boat diesel site |
| pdecat |
Posted - Apr 25 2012 : 09:11:38
Pascal:
Thuds 20hp per gallon per hour is correct for 4 strokes. I suggest rechecking your calculation as 10 hp per gallon is low even for gassers. Just for drill i checked cat 3508CTA and they are spot on and anything more than about 20 would be extremely overloaded.
If the DD are two stroke then they will use a bit more fuel.
n.b. to everyone. 20 Gph per hp means 20 gph per HP actually used but it is a fairly consistent number from which you can estimate how much hp you are actually using.
I fully agree that 10 kts would be above an economical run speed for a 42 and probably resulting in some bow lift which you want to avoid for economy, 8 should be better. 2 + mpg is what I would expect at 8kts with 4 strokes, a bit less with 2 strokes. |
| L. Keith |
Posted - Apr 25 2012 : 08:13:51
Call you local Detroit Dealer and get the fuel burn curves for that series engine, with the injectors that are installed in your particular engine. You may be able to find it on the web somewhere. You will have to adjust the "book number" for winds, current, ambient temperature and your particular vessel but the book number will be close. |
| PascalG |
Posted - Apr 25 2012 : 07:52:35
"5 Gal/Hr/100 Hp"
Not sure it works for all HP... That would mean the 1400hp cats in the boat I run would burn 70gph each at WOT... They burn almost twice that much
As to the OP, first there is a HUGE difference between 8 and 10kts! On a boat that size your hull speed is likely around 8.5 kts, anything over and you res tarting to push a big wake. At 10kts, you re probably burning close to twice the fuel you would just below hull speed
There is just no way you can get 3 NMPG at hull speed, or even 2.5. If you back down under hull speed, 8kts or just under 8kts then yes but I d worry a bit about going to slow with those pretty high strung engines. 450hp is really at the limit for 671s, you dont want to run them to cool and be very careful not to overload them. Make sure you re not overpropped (they must turn rated rpm at wot, should be 2300 like most DD but check) and avoid cruising above 2000
What most people dont realize is that a half knot above hull speed makes a lot more difference than the engine model. so find the RPM which will give you 8.75 on the GPS on a calm day with no current, stick to that and check your fuel burn by refueling after a couple of hours at that speed |
| OLD HOUSEBOATER |
Posted - Apr 25 2012 : 07:30:30
How much of a current was helping you? |
| abalmuth |
Posted - Apr 25 2012 : 06:44:57
Thud's numbers are for full load and are spot on for my 660HP Cats. 33GPH at full load |
| knotheadcharters |
Posted - Apr 25 2012 : 06:39:36
I have heard something similier at WOT, that being said you would have to be using the full 450 hp of the motors and I dont think that you would normally. The only real way is to install flowscans, which I probably will. The Admiral and I plan on some extended cruising in the very near future and with fuel prices I want to be able to maximize range and pre-plan fuel stops for the best pricing. In reality, it doesn't matter but I like seeing what I can get out of it. |
| Audrey II |
Posted - Apr 25 2012 : 04:48:17
quote:
Originally posted by Thudpucker
I was always told the Diesel's burned 5 Gal/Hr/100 Hp.
So 450 Hp should burn 22.5 (theoretically) per hour.
I don't understand these numbers is this at WOT? I have 420 Hp Cats and I don't burn anywhere near that number. |
| Thudpucker |
Posted - Apr 25 2012 : 01:05:34
I was always told the Diesel's burned 5 Gal/Hr/100 Hp.
So 450 Hp should burn 22.5 (theoretically) per hour.
|
| knotheadcharters |
Posted - Apr 24 2012 : 22:51:22
The rpms are between 800-1100 depending on current.
|
| Ghost |
Posted - Apr 24 2012 : 22:08:51
8-9 knots on my 45K pound 48 Tolly gets me around 2.5 MPG
I think 3 may be a touch high, but just. |
| knotheadcharters |
Posted - Apr 24 2012 : 21:10:51
Yea thats what I am thinking but kinda hard to believe. I've read anywhere fom 2.5 gph to 10gph at these rpms depending on where you look. I would install flow scans but that may give me a heart attack when I crank it up.
|
| Audrey II |
Posted - Apr 24 2012 : 20:46:43
How many RPMs is 8-10 kts?
I would be jumping up and down with those numbers! |
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