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Alex9797
21-02-2006, 10:48 AM
Hi all,

I have recently purchased a Cruisecraft 575 (2002 model) fitted with a Merc 150EFI engine also a 2002 model. Over the weekend i drove the boat from Horizon Shores marina to Peel Island and back a trip of about 60 k I think and used 60 litres of fuel ( unleaded). Does this sound about right?

In terms of weight the crew consisted of me , wife, and two small children all up around 200kg and a full tank of fuel 160 litres. The boat has just been serviced.

I sat on about 3800 rpm on average for the trip at about 44kmph. I am playing around with the trim a bit so i guess that this may have contributed to some variations. One of the reviews I read on boat point suggested that the testboat achieved 100kmph. Now either my boats a complete dud or the tester had a liquid lunch before the test. He also states that a speed of 60kmph could be acheived at 3000 rpm with a 150 on the back :o

I would be greatfull of any assistance as the wife is already starting to compare the cost of a day out on the boat with other non essentials like food and clothing :D.

ta

Alex

frankj
21-02-2006, 11:12 AM
Alex

I'm not sure how much your boat should use, others with similar boats may be able to help. There are so many variables of wind, waves, trim, efficient planing etc.
One thing I could suggest is the fitting of a Navman fuel monitor, this will let you see exactly how much fuel you are using in Litres/hr at any point in time and adjust your speed or trim to give you the most economical cruise speed.
The cheaper model 2100, is about $300. The more expensive model 3100 will allow you to connect a gps or paddlewheel and display litres/Km which will give a much more meaningful figure for economy.

Hope this helps
Frank

revs57
21-02-2006, 11:24 AM
G'day Alex,

I've got a 2005 150 efi Merc on a 6mt riptide (6.6 in other boats)...i reckon you are doing better than me at similar revs...I'd be happy with a litre per klm, but I know I'm using somewhere around 45ish litres/hr at 3800rpm

I raised the motor one notch for the last trip and it improved things a little, next step is to drill and cup the prop to tune it in...its over propped by 500 rpm...5000rpm at WOT want to lift it to recommended 5750...that may help too...but It will be changed over to an F200 Yam when the minister for finance approves the purchase.

I'm going to put a fuel flow metre/mamnagement system in to try to get the optimum fuel consumption...but she's a thirsty blighter

For the moment our trips are going to be a little more expensive than i had hoped

Cheers

rhys

bidkev
21-02-2006, 11:35 AM
Alex, I'm not familiar with your craft/engine but you may draw some comparisons from my Sea Legend 650 with a 220 mercruiser stern drive.

At 3000 revs, she pulls 28 knots, thereafter she increases 1 knott for every 100 revs, so at 4800 revs she is moving at 46 knots with 2 adults, full tank (210 litres) and 4 kids. At my rough reckoning I would say she does 85ks at 4,800revs. I haven't taken her above that yet, but I think she may be able to near 100kph.

Running at an average of 3500 revs the thirsty bastard consumes 1.3 litres per kilometre :o :o

kev

Money will buy you a pretty good dog, but it won't buy the wag of his tail.

Alex9797
23-02-2006, 10:49 AM
Thanks heaps guys :).

I guess that I was led to believe that this engine would use less fuel than this oh well. I am very happy with the instant starting and response although i wouldnt say that the engine is any smoother necessarily than carby models untill you hit a sweet spot at about 3700 rpm.

The boat does have a Navman fuel monitor, I will take the boat for a run on Saturday ( maybe to the M&G at Blakesleys) and try to work out how to use it.

Hey Kev that is one very quick rig. Not so sure that my navigation skills are up to travelling at 80kmph just yet. Am I correct in assuming that a 220 stern drive is the same power output as a 220 outboard?

Rhys, when the boat was seviced the mechanic took the boat for a run and got about 5400 rpm wot. He thought that this was ok with a stainless vengeance prop. Have you had any dramas with the sender unit for the trim gauge?

I still find it improbable that this boat can achieve 60 kmph at 3000 rpm with a Johnson 150 on the back. Maybe I should ask the people at boatpoint.


ta Alex

MulletMan
23-02-2006, 12:12 PM
Revs has a good point re the prop.
If you get a stainless steel cupped prop you can expect about 10% improvement in fuel as all alu props "flutter" at high RPM and become somewhat inefficient in the performance department.
Catch is that a good stainless prop will be around the $500 mark maybe but a great investment as they are almost impossible to bust and much better for performance.
Get yer missus to buy you one for "safety" sake - that always works for me!

Alex9797
23-02-2006, 12:29 PM
Good advice about the safety aspect Pink. Thats how we went from a 15 ft tinny to a 575 outsider :)


Alex

revs57
23-02-2006, 04:41 PM
Yeah hi Alex...5400 is probably in the window...if your mechanic is happy goodyoh....if it aint broke....

Yeah my trim guage is up the putty too, don't know if its the guage or the sender...working on that one

Cheers

Rhys

Sportfish_5
23-02-2006, 04:56 PM
You should not need a trim guage to tell when you are at optimum. Just listen and watch your tacho.


Cheers

Greg

kingcobe
23-02-2006, 05:41 PM
<snip>
Hey Kev that is one very quick rig. Not so sure that my navigation skills are up to travelling at 80kmph just yet. Am I correct in assuming that a 220 stern drive is the same power output as a 220 outboard?
<snip>

ta Alex

Yeah Alex, she's pretty nippy and turns on her stern too.

As far as navigation goes, I've let my skills wane a bit I'm afraid. The Gps projects a line of reckoned travel on the chart so I simply point the line (via the bow) as to miss sandbanks and the like and just steer that course. Never used the highway track yet but I'm going to familiarise myself with that soon. I make a note of the compass bearings so that if the gps packs in I can return via the old farts way ;D

I'm not that clued up on engines so I can't compare her to an outboard other than the fact that she "oversteers" ie "wanders" at slow speed. She's a V6 efi and I can hardly hear her at 3000.......turn her up a bit more and you can hear her slurping that juice though :o ;D After a 70 yammy two stroke running at 5500 it's wonderful to be able to talk to each other when underway without having to shout ::)

kev

If you want children to keep their feet on the ground, put some responsibility on their shoulders.

bidkev
23-02-2006, 05:46 PM
Sorry, last post was from me. The lad didn't log off again

kev

If you want your spouse to listen and pay strict attention to every word you say, talk in your sleep.

longtail
24-02-2006, 12:04 AM
i have a 2005 model 75st merc pushing a 480 allcraft challenger , i've found that if i sit on 4400rpm that gives me 28knts and returns about 2km per litre , if i push it higher than that i can get 34knts@5400rpm but economy drops to around 1km per litre.

cheers
jason

mark221263
24-02-2006, 08:53 AM
Hi Alex, my boat although a different model cruise craft should be a good place to start and provide a reasonable comparison.

I have a Cruise Craft 580 outsider (1992) running a 1996 Mariner 150hp 2 stroke, 2 litre, carby with about 280 hours. Your boat is a bit smaller, quite a bit lighter and easier driven than the 580. Also even though your outboard is a 2.5 litre injected model it should provide similar economy and better bottom end torque due to the extra 500cc and taller gearbox ratio.

WOT range for both outboards is between 5000~5600 by the merc manual.

I run either a 17” Pitch merc offshore 4 blade prop or a 17” Pitch 3 blade Vengeance 3 blade prop. The offshore prop provides better hole shot and low speed planing while also appearing to be less effected by boat loading. It does, surprisingly enough allow the outboard to rev a bit higher at WOT to 5800 and needs about an extra 200 rpm for the same boat speed as the vengeance prop. I don’t know hwy this is but the vengeance prop does appear to have more cup on the trailing edge of the blades.

One other thing to remember is that the 2 litre merc/mariners run a 2:1 leg reduction and the 2.5 litre has a 1.87:1 reduction so the same prop should push your boat faster by about 6% faster with all things being equal at the same rpm.

As far as the speeds go in the suggested boat report, this is absolute cr#p. There is no way a 150hp outboard #could have that amount of torque to push the boat at those speeds at 3000rpm regardless of prop pitch, a top speed of 100kph would need in excess of 225hp,

For my boat using the 4 blade prop which I run with the most I get the following speeds

3600rpm = #38~40 kph
4200rpm = 47~49 kph
5800rpm = 68~70 kph

The 3 blade vengeance gave a top end of 71 kph at 5600 rpm.

Fuel economy is as close to exactly the same regardless of either prop with the only difference being the 4 blade running an extra 200rpm for the same boat speed but with the outboard loaded up less.

My sweet spot for best cruise is 4100~4200 rpm which returns on average 1.35 klm / litre if the weather is good. At worst I have seen 1.05 klm/lt sitting on 3400 rpm in some really crappy weather off Frazer Is. The best I have seen was 1.45 klm / litre with full 160lt fuel, wife and 2 kids on a trip to Cleveland / Tangalooma and back on a millpond day.

With your boat being lighter and having a more efficient hull to the 580 as well as your merc being fuel injected I would of expected your performance to be slightly better than mine by 3~5 kph and the fuel usage to be the same or better. Your 5400rpm WOT sounds perfect, I would not change anything there apart from playing with outboard height.

I’ve pm’d you my mobile number so feel free to call if you want to discuss further.

Regards Mark
:)

Oldyella
24-02-2006, 02:41 PM
There is a USA rule of thumb for Economy on all 2 strokes.
It goes 10% of HP in US gall per hr at WOT.
I've calculated it here..
Your motor is a 150. Your top speed is @40 knots (about 73kph)
Converted from US gall to Aust 3.77-4.54, Knots to MPH 1.15 and mph to KPH 1.6
Drum roll......... 6.90 MPG or 2.4 litres per km
She seems a little too thirsty..

ahoj
24-02-2006, 05:06 PM
Alex-- anyone that can afford $100 a day or like $200 with depreciation boating with car travel and owning a boat with 150HP efi motor should not thake any notice of wifes nonessentials.. In time-you will be restricted with your boating to 1-3 trips a year..and you will have to follow the rules..... and like it...... ;D

Ahoj