Speed, Engines, and Fuel Economy.

[fishman7]

hi
a fathom is 6 ft.i have twin 200 2 stokes 4000 rpm give me 20kts i go thought 100lts for about 2.5 hr running around.at 5000rpm i get 29 kts but use a lot of fuel the boat is about 3.5 ton 33ft shark cat.
danny

[bidkev]

One of the things I hate is the use of 4 different measures.

litres per k
litres per kn
miles (nobody apart from yanks and pommie gits use that (sorry Kev)
litres per hour

Most of us recognise one of these. But the we have to either try to convert it in our heads, or have no idea what it means so have to disregard some of the posts.

In this metric age, I would have thought litres per k would be the best of the bunch for the average fisho to relate to. At least then I would understand every post. 30 litres per hour means nothing to me. Miles sort of do because I know the 1.6 conversion. kn I guess to be about 2 k, but as indicated above, that is not correct so need a calculator whenever it is mentioned.

So my vote it to adopt k per litre as a standard in ausfish discussion.

Cheech

I'm offended NOT!

Yeah, I know where you're coming from Cheech. My guage reads in miles and Ks but it doesn't say whether it's nautical miles. I have to assume that it is, considering it's on a boat

It would be easier if it had a trip meter on it 'cause I could relate better to mph or kph but it doesn't even have a running time clock on it. I have to keep a bloody diary of how many hours I've run it and when you're toing and froing chasing macs that can be a real pain to remember at the end of the day. I am going to fit a clock to it at it's 20 hr service though so that will be one problem less.

I could check the miles/ks covered (to find out litres per mile/k)by setting the gps to track and check the tracks up at the end of the day but that would be a pain as well. and I don't like the track marks on the screen. At the end of a day trolling or chasing macs it would look like a cat with a ball of wool

<thinks> Must check manual regarding tracking mode to see if tracks can be hid?

kev

[Mantaray]

hi
a fathom is 6 ft.i have twin 200 2 stokes 4000 rpm give me 20kts i go thought 100lts for about 2.5 hr running around.at 5000rpm i get 29 kts but use a lot of fuel the boat is about 3.5 ton 33ft shark cat.
danny

3.5 ton 33 ft shark cat? Is that right?

[scuttlebutt]

3.5 ton 33 ft shark cat? Is that right?

is it so hard to believe?

http://montereybay.noaa.gov/research/sharkcat.html

cheers,

steve

[Mantaray]

[quote author=Mantaray link=1128320700/30#32 date=1128657051]
3.5 ton 33 ft shark cat? Is that right?

is it so hard to believe?

http://montereybay.noaa.gov/research/sharkcat.html

cheers,

steve[/quote]

Sounds a little long for the weight or a little light for the length. A 28 foot shark cat has a hull weight of 3000kg alone and the 3500, 9.3 metre, 30.5 feet displaces nearly 5 tonne. So yes I am querying if 3.5 ton 33 feet is what it is meant to be?

[redspeckle]

kingtin
I have agree with sea saw it does depend on the sea condtions more rough it is more fuel used
One thing I have notice in the bay motor works less, Going through the south passage works very harder then out offshore works hard or harder depending on sea condtions
I have V4 90 2 stroke when heading out in the morning set on 3000rpm to 3500rpm then in afternoon 3.500rpm to 4300 rpm keen to head home quickly I am lucky just push 17.5 ft plate boat not big heavy fibreglass boat
Speed vary's from 20km/hr to 45km/hr and fuel use between 60 to 90 litre's doing from 100km to 130 km depening on offshore condtion and crossing the bay ( wind and swell + tide running direction for bay & offshore + bar crossing and which passage go through )
Mitch

[hoga]

TESTED MINE TO DAY 620SF # 175 2ST FULL FUEL 200LT+ 220LT WATER TO WEIGH IT DOWN A BIT
3000RPM 17KPH #0 . 7 #KPL
3500 39 # 1.1
4000 51 # 1.3
MAX RPM WAS 4600 # # IT HAS A SOLAS 4 BLADE PROP #19 INCH
GOT SLIGHTLY WORSE WITH THE 3 BLADE ON
DO YOU THINK IT IS OVER PROPED WOULD LIKE TO GET BETTER ECON BETWEEN THE 300O & 3500 HOGA

[SeaSaw]

Hoga,

If your only getting 4600 max rpm from that prop then is is way over propped for the load you are carrying. Check your outboard manual to find out how far it should wind out to, but I would guess that it should go to around 5500.

Cheers,

Mark

[dfox]

[quote author=Mantaray link=1128320700/30#32 date=1128657051]
3.5 ton 33 ft shark cat? Is that right?

is it so hard to believe?

http://montereybay.noaa.gov/research/sharkcat.html

cheers,

steve[/quote]

I worked on a 9.8 meter cat pro fishing, it had inboard desiel engines that would be a fair bit heavier then there outboard counter parts, in light ship it wieghed just under 6 tonnes. i agree 3.5 tonnes is a little hard to comprehend. Either our boat was built tuff or the shark cat was made paper thin?

[dfox]

Your right there mark! 4600 max revs is a major concern hoga, that setup may do damage to the engine ...foxy

[fishman7]

hi guys
no 3.5 ton is right it was 28 ft but we put a 5 ft pod on it. to keep it light.we also only had about 300lts of fuel in it at a time.but if we had it full of fuel it hold 1200lt and them 10 poeple she start to feel it.these a cat up from us its 33 ft also but its 6.5 ton its a cougar cat
cheers
danny

[Mantaray]

hi
a fathom is 6 ft.i have twin 200 2 stokes 4000 rpm give me 20kts i go thought 100lts for about 2.5 hr running around.at 5000rpm i get 29 kts but use a lot of fuel the boat is about 3.5 ton 33ft shark cat.
danny

100 litres for 2.5 hours? That's go to be extremely good for a pair of 200 2 strokes, 20 lites an hour each and is that doing 20 knots?

[bushbeachboy]

70 4 stroke Suzi, fairly new boat and motor, one trip 49 nm for 62 litres, filled before and after trip.

[2iar]

70 4 stroke Suzi, fairly new boat and motor, one trip 49 nm for 62 litres, filled before and after trip.

Hi Mate,

I'm getting one of these put on the new boat (Signature 460DF) - your figures aren't too bad. What size of boat do you have it on, if you don't mind me asking? I like the fact that the 70 has the extra grunt, but no more weight than the 60.

Thanks,
Mike

[bidkev]

Just got back from a bummer of a trip, the only consolation being that my petrol usage has improved dramtically.

Haven't worked it out yet but Shorncliffe to Mud at 10 knotts........yes 10!..........I'd no sooner left than it blew a bloody hooley and I had to go shelter there overnight. From there to Curtin at 38 knotts, then back to 4 beacons at 38knotts, then back to shorncliffe at 38 knotts. 70 litres.

I had the engine trimmed at neutral which supposedly gives better forward thrust as opposed to screwing up or down and trimmed the boat with the trim tabs. That's the theory I read about but I suppose that once you trim with the tabs the engine (prop) isn't perpendicular anyway?????

I also, normally trim so that I'm just short of porpoising but that then gives more stern drag on the water that it otherwise would sitting with bow lower down, so I trimmed bow lower than I usually do. Hope I'm learning here and someone isn't going to rubbish the theory I got it via google, honestly

Anyway, It seems to work as that consumption is way less that I've been doing.

cheers

kev