Noosacat economy

[Flex]

Hi all.
Chasing anyone who owns a 2300/2400 Noosacat and their current fuel economy.
I have F150 yammies on mine.


I’ve just finished trialling a set of 4 blades in the hope of improving economy and it made things worse.

Yes they are a heavy boat but I woukd have thought I’d get slightly better economy than what I do.

I currently get 0.85km per litre (at best)
I trialled 4 blades and did 206km for 246l for fuel.( 17p 4 blades)
That was running in ‘economy mode” 4000 rpm for 48-50km at 55-57l .(pisses me off to run so slow) 4400rpm was 55km/h @ 72l.. so that’s 0.7km/km. Terrible.


With the stainless black 3 blades I was running 4400rpm @ 60km for 70l hour. More my style but not great.

I’m wondering if the f150 yammies are just a thirsty engine?
Surely the 2300noosacat isn’t that much heavier (maybe couple hundred kg at best)than 2400KC.
They seem to get great economy and awesome speed from the 140’s.

Anyone have a similar boat and can share exact fuel usage?
Not many blokes have precise fuel burn figures.
I often run 400km round trips so fuel usage is a concern.

Cheers.


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[Noelm]

Can't really help you with economy, but, a couple of my mates have F150s and their fuel use is fine.

[Cape Crusader]

G'day
I think it's possible that your NC is under powered with 115's and they are working a little hard
Cheers
Rod

[Flex]

G'day
I think it's possible that your NC is under powered with 115's and they are working a little hard
Cheers
Rod

No I’m running f150 yammies.


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[Cape Crusader]

[QUOTE=Flex;1645963]No I’m running f150 yammies.


Ooops, I still reckon I can do without glasses, but .....
Cheers
Rod

[soulfish]

Flex I was running the 17px13 3/4 black props on my 2700nc..switched over to the 17 reliance yammy props..they were around 5% better on fuel..i run the reliance still on my new 4cly 200 yammys now..was getting around that 1.2ltrs to 1.3ltrs a klm with the 150s..but it did vary depending on load..up to 1.4ltrs per klm for a trip to 1770/breaksea with a very heavy load and 700ltrs of fuel on board..

[rexaway123]

On my 2012 2300 with 150 yammies
On an average day going slow, fast , trolling then run home etc
Use just bit more than 1:1
So on say a 150 km day will use about 160-165 litres
Running 4 blades

[Flex]

Cheers for the replies.

Yeah I tested set of 4 blades the same spec as your running Rex. Was very disappointed. Less speed. Worse economy. Getting 0.7km/litre at 4500 rpm. Terrible.

Going back to 3 blades and see what happens


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[scottar]

Not sure how it would pan out on a cat but a large blade area 3 blade gave me the best economy mid range by a pretty significant margin. I'm now running a BRP Rebel prop which is similar to the Mercury Mirage Plus. Not sure if Yamaha has an equivalent.

[rexaway123]

Don't know why your result could be so different to mine
I lost no speed either
Weird

[gazza2006au]

700 litre fuel tank!!!!! how on earth do u explain that fuel bill to the wife, with a fuel tank like that i would only need to fill up once every 5 years ;D8-) i'd be broke for the next 10 lol

[Flex]

Don't know why your result could be so different to mine
I lost no speed either
Weird

Yeah very odd. Motors are on top bolt hole.
Rex do you have any speed figures at 4000 or 4500 rpm? Unless the turbo offshores are very different than the powertech. What max rpm you get.?
I’m gunna test a set of 20’s and high cup 19’s.

[Noelm]

I guess the motor height is OK?

[Dignity]

Have you checked for water in the hulls, I know AL from Seatrek has drained a couple of them. He has a special drill bit to go right up the front of the hulls where the wate is tends to pool.

[Flex]

Thanks for the suggestion. But I have port hole access to every compartment. No water.
Possibly being ex-rescue it’s heavier.altgough I don’t think that’s the case as all Noosacats are built the same I believe


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[Darren J]

Try Mick (outta line). He has a 2300 walk around with 150 verados. Had a bit of grief with handling until props were sorted I think. He could tell you where his economy is I am sure. Maybe pm him. Not sure if he gets on here much.


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[Homer_Jay]

I have a 2400 that is quite heavy. I get pretty much spot on 1lt/km all the time.
Even when fully loaded for a few days out at the reef with 600lt fuel/water/camping gear/ect it doesn’t change much.
Twin 175 Suzuki’s

Yours sounds a bit thirsty, but depends how you drive it too. If I drove mine harder it would be same as yours.

[soulfish]

700 litre fuel tank!!!!! how on earth do u explain that fuel bill to the wife, with a fuel tank like that i would only need to fill up once every 5 years ;D8-) i'd be broke for the next 10 lol

Gazza...what she don't know wont hurt her..i think in there language its..4 hair doos & nails

[Dignity]

Gazza...what she don't know wont hurt her..i think in there language its..4 hair doos & nails

Or 4 pairs of shoes

[gofishin]

Yeah very odd. Motors are on top bolt hole.
Rex do you have any speed figures at 4000 or 4500 rpm? Unless the turbo offshores are very different than the powertech. What max rpm you get.?
I’m gunna test a set of 20’s and high cup 19’s.

First thing I was thinking Flex was motor height comparison, given they are the same boat - albeit with assumed same weight. Top hole or motor at top position (ie bottom hole)?

Exact same (diam & pitch) 4 blades on both boats? Or just both 4 blades? What type did you try? Sometimes you can jag a sweet change in props with one change, other times it can be damn frustrating.

I’ve also recently heard that 2400 NC’s are running arse-about counter rotating than normal as that provides better handling and prop tuning - at least with the selective rotation Zukes.

Don’t give up mate, can be really frustrating but the end gain is usually worth it [emoji16].
Cheers
Brendon


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[Flex]

Thanks brendon.
Regarding motor height it’s as high as it can possibly go.
Props were a different brand but exact same specs. 17p 14,1/4.

Funnily Noosacat has a boatvtest report on their site with my exact setup when I had the 3 blades on.

Must be like a new Car report where the figures are exaggerated. Because I get no where near what Yamaha states.

Their results are
4500rpm for 61km for 61litres.(which is good economy)

My results with identical setup is
4500rpm 61km for 70litres.

Running light to, gets smidge worse when running heavy.

I’m swapping my 4 blade 17’s and gunna try set of 3 blade 20’s.

See if I can jag more speed for the same fuel burn.


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[Noelm]

Maybe even though the motors are as high as they can go, they are still low?

[Andy56]

the one bit of info you havent provided was the rpm at wot. You would want to get the full rpm range on the prop. all this talk of going from 17" to 20" would have me worried. I dont think there is much difference between a 4blade 17" and standard as far as ouright speed or economy goes, your just changing the points of power delivery. Going to 20" is just going to bog you down. I would be inclined to go 15" to make the motors boogie. I dont understand the fear of over reving as they all have some kind of over rev control, but getting bogged down or inadequate performance is somehow more acceptable. Smaller pitched prop means the motor spins easier and has less load which should equate to better economy. Dont think that because its a yamaha it should have the same sized props as other makes.

check this out https://www.youtube.com/watch?v=CFF6yL9lX9A

And those videos that show the yamaha motor not being able to get the boat on the plane, ha, bullshit artists. Drop the prop size and it will !!

In your case, your only interested in the 4-5000rpm range so I wouldnt worry about topend speed so much.

[gofishin]

...
Regarding motor height it’s as high as it can possibly go.
Props were a different brand but exact same specs. 17p 14,1/4....
Re motor height, see Noel’s reply. Are they still too low? Do they ventilate easy at normal trim or not at all? How much +ve trim before they let go?

Prop pitch in any prop size is ‘an estimate’, unlike the diameter, which can be physically measured. Different brands same size spic means they will be close, but not the same. Can you try/borrow another set of props on the same boat/model that you know work better?


....Funnily Noosacat has a boatvtest report on their site with my exact setup when I had the 3 blades on.

Must be like a new Car report where the figures are exaggerated. Because I get no where near what Yamaha states.... Are you comparing stats from ideal conditions (where there’s will be tested - in the river probably), or your real world conditions?

Boat weight? If yours was a rescue boat then it definitely was built to survey and was obviously ‘in survey’ for some time. Could easily be heavier than a rec boat same model. Wheghbridge is the only way tri know.



...I’m swapping my 4 blade 17’s and gunna try set of 3 blade 20’s. ... That’s a huge jump in pitch! I doubt they will work well unless the 17’s are under propped, and/or they are a tall prop and the 20’s are short. But try them anyway.



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[feral cat]

Flex i'm the same mate, just bolted on F150's on a 660 noosa cat (simular weight) Built bigger pods to float them.
Very dissapointed in econemy, The noosacat tests are with 110ltr of fuel and in the creek which is a dead set wank. I have just trialed a set of powertech 18's and in calm conditions in tin can straights i averaged 1.08ltr a km and hit 45 knts full fuel with the cook and kids driving it reasonably hard. Thats good i would have thought, but recently i did a trip in some swell and it all change. Did 318km for 430ltrs. 1.35ltrs a km driving like a girl,22 to 24 knts until we came home at 28knts which the boat felt happy then and burnt less juice for the trip home which makes me think i need to go back to a 17 with less cup. Frustrating as f@@k mate especially when blokes with 2700's are getting 1.4ltr a km and another 2700 i know of getting 1.5ltr a km, then theres a 3000 series KC i know of and he gets 1.5 to 1.6ltr a km.
I'm trialling 4 blades 16's soon as i need eco more so than speed as i cant sit on 30knts everywhere off fraser and range is a higher priority.

Rexaway...Out of curiosity what was your fuel figures swinging the 19 standard black prior to you going 4 blades?

[gofishin]

...I’m wondering if the f150 yammies are just a thirsty engine?
Surely the 2300noosacat isn’t that much heavier (maybe couple hundred kg at best)than 2400KC.
They seem to get great economy and awesome speed from the 140’s...
I wouldn’t say thirsty Flex. Strong, yes (check the EPA test data), but no thirstier than any other ‘same gen’ four stroke.

The boat specs available online show that there is approx 350-450kg difference in these boats with max rated donks (NC heavier), and from observation of boats, std fitted motors, trailers and tow setups over the years, and performance figures etc, I would say this indeed the case. Slightly different hull design too.

A mate in my fishing club has a NC 2400 with 150 Zuke AP’s. Sub 1km/L if he travels too slow, but around parity or 1.1 occasionally if at 50k’s and calmer conditions. Another guy I know with same boat, slightly heavier but 175 AP’s gets marginally better economy I think (0.1), but is also running a pitch larger props (due to extra HP). No precise stats sorry.

One thing is for sure, from my research and recent mates motor upgrades, is that the ‘current gen’ 4/‘s are indeed 10-15% better on fuel, and across all brands too. And, E-TEC G2’s a lot better than G1’s etc. Would it warrant an upgrade on economy alone? IMHO, no, but if factoring in other +’s (incl range), maybe [emoji6]).


...Anyone have a similar boat and can share exact fuel usage?
Not many blokes have precise fuel burn figures....
I can now [emoji16].

Similar, yes, but bigger and heavier, and a different hull design - but still a cat [emoji38]. 2018 Powercat, real hull size 7.6m(25’), plus pods x 2.8m(9’) beam x ~3000kg dry hull weight (weigh bridge, give or take a few kg’s depending how close the trailer TARE is to the plate). Hull design itself hasn’t changed in 30yrs, and is the same as the old Powercat 268’s. Zuke 200AP’s, 3 x 16 x 20 Zuke props.

Some recent performance figures in glassy conditions, which from other trip stats, counteracted the reduced crew weight anyway as she was sticking to the glassy calm water a bit [emoji1].

These figures were with just me on board, only 15 hrs up on the donks, ~250L fuel & ~120L water, ~ 125kg gear. On other days with 4 or 5 adults and a lot more weight/liquids, the figures at 25 – 30kn don’t change much from below even in 15-20kn Moreton Bay conditions – at least from what I have seen anyway.

All the readings below were from the gauges except for the last column [km/h], which I calculated as I didn’t write them down. Fuel data is the combined Total for BOTH donks.

rpm, kn, L/nm, km/L, L/h, [km/h calculated]
3000, 15, 1.8, 1.0, 26.4, [28]
3200, 18, 1.5, 1.2, 28.6, [33]
3400, 20, 1.5, 1.2, 31.2, [37]
3600, 22, 1.5, 1.2, 33.8, [41]
3800, 24, 1.6, 1.1, 38.6, [44]
4000, 25, 1.6, 1.1, 42.8, [46]
4200, 26, 1.8, 1.0, 47.2, [48]
4400, 27, 1.8, 1.0, 49.0, [50]
4600, 29, 1.8, 1.0, 54.7, [54]
4800, 31/2, 1.8/1.9, 1.0, 60.4, [57]

In comparison to my last boat (685 + F250, pics attached for size comparison)... ‘IF’ conditions allowed, and I could travel as fast in the old girl, there would be no difference in economy! Brilliant performance really, especially considering the cat is ~1100kg heavier dry, and has 400HP instead of 250!

A mate owned the same hull boat, with 2007 model 200 V6 Zukes, and I am about 20-25% better economy it seems with the 4 cyl AP’s. So... the current gen donks are indeed very good with performance/economy.
Cheers
Brendon 118296


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[scottar]

Smaller pitched prop means the motor spins easier and has less load which should equate to better economy.



Not necessarily correct. I have found exactly the opposite with my E-Tec. Because it has such high torque, it will quite happily punch the boat out of the hole with a prop that is too high in pitch (to a point) and return fantastic economy numbers. The best numbers I have seen were with a prop that resulted in WOT rpm being 500 revs below "optimum". I ended up settling on a prop that gives a WOT of 200 revs below optimum. The closer I get to optimum, the lower my best economy numbers go and going over optimum WOT rpm with too smaller pitch produced woeful results.

Talking to various boat builders back in the day when 4 strokes first started coming into vogue led to an opinion that provided the weight penalty is not significant enough to induce handling issues, you get better results by fitting higher horsepower so that cruise revs can be kept below the magic 3500 mark. There is more to it than just RPM though. If the hull isn't happy with the speed at a given RPM and isn't actually working efficiently, it can markedly decrease the economy. As such having a higher horsepower capable of swinging a bigger prop at WOT can in some circumstances put a hull right in it's sweet spot at a more economical RPM whereas the smaller engine with a smaller prop is running outside it's most economical RPM range to generate the boat speed required to make the hull work - but can't run a bigger prop to the required RPM. It's a delicate balancing act at times.

[Lovey80]

Completely agree Scott. It’s probably more relevant to cats too. They need to be moving at a certain speed before they become efficient. Each cat design will be different and some are better than others. I know with mine the speed is around 22-23knots. From memory with the little 60’s that’s at about 4700RPM. Some will consider those to be very high cruise RPM but they seem to do it effortlessly and the economy reading constantly flicks between 1.4 and 1.5km/l. Which of course is crazy good economy running twin engines of any size. The fuel used for km traveled marries up also. For a 135km trip I’m always around 100litres used when I fill up and that takes into account a lot of time with them idling while drifting, pulling anchor etc.. WOT of 29 knots @ 5800RPM drops it back to 1.3Km/L

[hungry6]

Yep, I also can attest that cats produce the best economy above 20kn, but not WOT LOL. Also lifting the nose up also help a fair bit and crazy enough it uses more fuel in glass out condition as to sea with around 10kn wind. My twin 140s get about 0.8 to 1 Lt per kay depending how much of a hurry I am in, and I consider myself to be a lazy boater, mean I set and forget and just turn the wheel.

[feral cat]

That is some unbelievable fuel economy gofishin your getting. I have early mod 2016 F150XB's on my cat and there 10% worse than my 02 mod mercury 115;s on fuel. I'm a tad worse than flex on fuel economy as well.



Trialing the same 4 blades soon on a loaded trip to see if it makes a difference. The 3 blade 18's would lug in the arse at 24 knts and feel a bit boggy in swell when loaded on a trip. Hoping the 4 blades will lift its fat arse in the midrange revs in swell and keep her up. i will let you know how i go.

[gofishin]

Wow feral, 10% worse is very strange, especially considering the generation(s) gap in the donks! What cat and how much heavier are the XB’s? Props definitely sound wrong, maybe motor height too maybe - as that’s a very unexpected performance penalty.

Yeah, stoked with mine. Time will tell I guess, the real figures will be revealed when I can get her ‘fishing ready’ and do a big loaded trip etc.
cheers


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[feral cat]

Wow feral, 10% worse is very strange, especially considering the generation(s) gap in the donks! What cat and how much heavier are the XB’s? Props definitely sound wrong, maybe motor height too maybe - as that’s a very unexpected performance penalty.

Yeah, stoked with mine. Time will tell I guess, the real figures will be revealed when I can get her ‘fishing ready’ and do a big loaded trip etc.
cheers


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660 noosacat, simular size and weight of the 2300 series that flex has.

I have added about another 100kg on the bum with the xb's. Fuel econemy was worse from the get go with spinning A few different props.
Built bigger pods to suit and still no difference to econemy. I took the 14 1/4x17 four blades for a run it feels weird as buggery. Huge arse lift (which is there claim to fame) and felt like i had run out of trim to lift the bow. Hit 40knts at 6000rpm
Ill keep them for a loaded trip and see how they go on eceonemy. The 3 blades would drag its fat arse in swell and burn excess fuel. In calm conditions i would get good eco but unfortunately off fraser island its rarely flat. Lol

[gofishin]

What about motor height feral? Two different brands can both be the the nominal ‘XL’ etc, but can regularly require different bolt hole mounting due to differences in actual motor dimensions and number of mounting holes etc.

Have you tried raising the donks? With plates parallel to the hull plank, how much higher are the plates? And how long are the pods?


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[feral cat]

Sorry flex, i dont mean to hijack your thread.

Gofishin i have had them up as high as they can go with cav plate 95mm above bottom of hull. Old pods were 400 mm long and we have taken them to 600 long and another 170mm wider. So engines are 200mm further back. Funnily enough fuel economy hasn't changed but i'm not sure i'm sold on the looks as i'm most likely going to pull back off and chop 90mm off the length but that's another story.lol
I have tryed 3 blades 18's on 2 different holes and the 17's on 2 to different holes and now the 4 blades on 1 hole down from the top (cav plate 75mm above hull). Just waiting on reasonable weather and time off to take her on a loaded trip but the 4 blades feel weird. Next step is back to 3 blades with a set of perms.

[Flex]

All good feral, hijack away:) I honestly think the design of the 150 yam isn’t for economy. Compared to the suzuki,Honda’s etc they don’t seem to have the tech for economy. Very basic engine , super reliable but low tech.
The 200 yam gets slightly better economy than the 150 due to VVT.
Those suzuki figures posted are excellent figures. I’d be stoked over those.

Also feral the distances you do offshore accentuate any economy issues.
A lot of blokes only do short trips so the economy can seem better than what it is.

I was going to test my 20p’s this weekend but cyclone is ruining my holiday!


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[gofishin]

Sorry flex, i dont mean to hijack your thread.

Gofishin i have had them up as high as they can go with cav plate 95mm above bottom of hull. Old pods were 400 mm long and we have taken them to 600 long and another 170mm wider. So engines are 200mm further back. Funnily enough fuel economy hasn't changed but i'm not sure i'm sold on the looks as i'm most likely going to pull back off and chop 90mm off the length but that's another story.lol
I have tryed 3 blades 18's on 2 different holes and the 17's on 2 to different holes and now the 4 blades on 1 hole down from the top (cav plate 75mm above hull). Just waiting on reasonable weather and time off to take her on a loaded trip but the 4 blades feel weird. Next step is back to 3 blades with a set of perms.

Yeah sorry flex, but I guess it is still on topic [emoji16].

Feral you have certainly tried a lot of height options, but that’s good, only way to tweak the best out of her! If you weren’t suffering any ventilation or performance issues I personally would keep them high, especially if you are adding permatrims.

As for the bigger & longer pods improving economy - I would expect only possibly if they were full hull extensions. 600mm setback is indeed a long way back, so 75+ above the plank doesn’t sound too high.

Re weird performance you mentioned up high, you could also try swapping the g/boxes over so rotation is arse-about. NC are installing like this standard now as it improves the performance They experimented with the selective rotation Zukes and found it was better, so I believe they are doing this across the board/all motors (per Wayne’s comment to me early in the year). Some yank cat manufacturers have been doing the same for a while I believe too.
Cheers


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[Smithy]

F150s have a following here on the Sunny Coast over the Suzukis. One mackerel pro I know changed from Zuke to Yam and has never looked back. They love the CCs being a 2.6 litre motor. I also remember Skipalong from here also thinking of going Zuke to Yam on his PPP for load carrying due to the gear box ratio of the Zuke. He was crabbing with it and a mackerel pro here had the same setup as him but with a Yammie and was doing way better figures. I know the guy I bought my Stabicraft off of had another one or two built after it and as he went though Leisure Marine when they were still around he had Hondas on the last few. I usually run into him at the boat show every year and some years he has them on display. I noticed he ran Permatrims on the ones with the 135 Hondas but he didn't need anything on my 140 Johnuki. The 135 Honda is the same CCs and weight as the 150 Honda isn't it. Not many Hondas here on the north coast. Few F150s on a couple of NC2700s here too, one spanner crabber and one deep drop fisherman.

[Moejoes]

Hey Feral,
I'm going thru exactly the same as you but on the NC3100 with twin 250 yammis.
I made up pod adaptor plates and bolted them under the pods to bring them back to where they were originally after being raised and found that the boat was very stable but fuel economy went south.
Obviously because I then created more drag under the boat.
I have now removed them plus the spray deflectors and the perma trims, tried 15", 17" & 18" props, raised the motors one hole, put the spray deflectors and perma trims back on.
The boat walks a bit but I actually prefer it that way. It seems to ride much better
I have now managed to get it back to something a bit more manageable but like yourself I'm also after range fully loaded and need the boat to do 30knots as that's the best performance ride for the boat.
I have data for 10 different set ups now and want to do a trial with a set of 19's but they might bog the boat down in heavy seas and be much worse economy.
It's hard to compare the data tho, as it's done on different days in different conditions.
Just need to do more trips to see what works best.
Perseverance will get us there ;)

[Smithy]

The torque curve on the 4.2 litre Yammies is weird. The shark net contractor here repowered original F250s for new 4.2 litre ones and had to dick around with props heaps even though it was same horsepower for same horsepower and they took a lot of getting used to. 10-15% better economy on that and a spanner crabber here who did the same on a Kevlacat, just they did totally different things at different revs with different speeds they were happy etc.

[Moejoes]

Smithy, do you know what props they ended up using?
I've tried 15-3/4" 15T, 15-1/2 17T, 15-1/4 18T & a set of 17" Lexor Plus.
My aim is to get 30 to 31knots @ 4200 to 4300 rpm.
This will give me the best fuel economy, distance travelled & optimum ride for the boat.
Currently got it running at 28 - 29knots, which is why I want to give the 19'" a run.
The motors are still in run in stage and I'm told they will get about 2 - 3 % better as they are programmed to run a little richer for the first 100hrs.
Cheers Rob

[Smithy]

I would have talked to Keith about it a few years ago. Next time I talk to the NC3100 guys I'll ask for you.

[Dignity]

I would have talked to Keith about it a few years ago. Next time I talk to the NC3100 guys I'll ask for you.

That is Keith's old boat, he's now moved on to a 41 footer and he has been involved in the trials.

[Moejoes]

Cheers Smithy


I would have talked to Keith about it a few years ago. Next time I talk to the NC3100 guys I'll ask for you.

[feral cat]

Yeah sorry flex, but I guess it is still on topic [emoji16].

Feral you have certainly tried a lot of height options, but that’s good, only way to tweak the best out of her! If you weren’t suffering any ventilation or performance issues I personally would keep them high, especially if you are adding permatrims.

As for the bigger & longer pods improving economy - I would expect only possibly if they were full hull extensions. 600mm setback is indeed a long way back, so 75+ above the plank doesn’t sound too high.

Re weird performance you mentioned up high, you could also try swapping the g/boxes over so rotation is arse-about. NC are installing like this standard now as it improves the performance They experimented with the selective rotation Zukes and found it was better, so I believe they are doing this across the board/all motors (per Wayne’s comment to me early in the year). Some yank cat manufacturers have been doing the same for a while I believe too.
Cheers


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Yeah mate the extra 200mm setback was a bit of a stuff up but im running with it for now. 2300's are 510mm long and for cosmetic reasons ill pull pods off and chop them again. Another issue i have is excessive spray going on the engines now at around 12 to 15 knts. We made the pods without the spray plate left on the bottom overhanging 100mm.

The economy is no better or worse now comparing to old pods, the extra 100kg on the arse must be enough to tip it over the edge in swell to get such bad economy. In swell it feels boggy and i can see the ltr/hr go through the roof. Thats why i think perms or 4 blades should help maintain lift at 25knts in swell and give better range. Funnily enough though with the 4 blades on the other day just mucking around in the wide bay bar i was smashing along at 30knts in slop for the softest ride I've ever felt in it. Felt like i needed a tad more bow up attitude but just couldnt quite get it there but i could plane at really slow speeds. Thats why im keen to do a loaded trip and see what the eco is like and ride etc before i put perms on and back to 3 blades for a trial. Ah flippen boats doing my head in. 😂

[feral cat]

Hey Feral,
I'm going thru exactly the same as you but on the NC3100 with twin 250 yammis.
I made up pod adaptor plates and bolted them under the pods to bring them back to where they were originally after being raised and found that the boat was very stable but fuel economy went south.
Obviously because I then created more drag under the boat.
I have now removed them plus the spray deflectors and the perma trims, tried 15", 17" & 18" props, raised the motors one hole, put the spray deflectors and perma trims back on.
The boat walks a bit but I actually prefer it that way. It seems to ride much better
I have now managed to get it back to something a bit more manageable but like yourself I'm also after range fully loaded and need the boat to do 30knots as that's the best performance ride for the boat.
I have data for 10 different set ups now and want to do a trial with a set of 19's but they might bog the boat down in heavy seas and be much worse economy.
It's hard to compare the data tho, as it's done on different days in different conditions.
Just need to do more trips to see what works best.
Perseverance will get us there ;)

Yeah mate its frustrating to say the least, I bought these engines because I wanted more grunt than the 115's but I also didn't want a beefed up 115 into a 140. I thought these would be better on fuel than my 02 mods as I want to start doing a few trips to the swains from 1770, hence higher cruise speed when I can and the f150's do it easy being a bigger cube engine. To bolt these up and have worse eco is disappointing. I'm going to gut the front of my boat as well next trip and lay anchors etc at the back with these 4 blades. I'm running powertech props and have been swapping them out since may this yr. Just recently they handed me about 5k worth of gear and sent me off to test. Can't complain about there service.

[gofishin]

The torque curve on the 4.2 litre Yammies is weird. The shark net contractor here repowered original F250s for new 4.2 litre ones and had to dick around with props heaps even though it was same horsepower for same horsepower and they took a lot of getting used to. 10-15% better economy on that and a spanner crabber here who did the same on a Kevlacat, just they did totally different things at different revs with different speeds they were happy etc.

Yeah completely different props required Smithy, and dicking around for sure. Actually the hp increased a lot between ‘250hp’ 3.3L and 4.2L variants. The 4.2s had ~24 odd hp more, but a massive ~70N.m more torque - albeit at higher revs (from memory, per EPA stats). Despite this substantial increase in both specs, the increase in prop speed via a change from 2:1 to 1.75:1 meant a 2” drop in pitch was reqd (and sometimes this was not quite enough). Also, per the theory, a slightly smaller diameter was beneficial. PITA when most of the good props around for them were originally designed with lower gear ratios in mind, and ‘past experience’ was out the window!
Cheers Brendon


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[scottar]

Question to the guy's that have tried a few different props - I have found with the props on mine that the blade geometry has been the single biggest facilitator in economy change. Going from 3 to 4 with a similar blade shape produced an improvement but nowhere near what going to a large blade area 3 blade did - even though the pitch variation required was a 2 inch drop (and it still dropped revs) - have you found similar results on a cat? Essentially the prop has much lower slip numbers at mid range RPM thus generating the required mid range cruise speed to make the hull do it's thing with less revs. It's effectiveness falls off as the RPM's climb though - WOT boat speed is down a few knots. I also found that the vibration level at "just on plane" was a bit higher - this could simply be this prop though - I haven't had it balanced as it's not really bad enough to worry about IMO.

[feral cat]

Well trialed 4 blade 17's and what a pig.
Had a P66 transducer mounted directly in front of prop with good readings, 2 test runs on the 4 blades with same weight same fuel etc in calm conditions. 1 run with tranny in front of prop, 1 run with it mounted to the side of hull.

[Snapperscott]

I've recently put Suzuki 140s on my 2300 walkabout and they are awesome. I changed from 19 to 21 props and get 30knots at 5000 for around 25l per engine. I was worried about the bullcrp about them being glorified 115s but I wouldn't swap them for anything. Especially when they are nearly 40kg lighter each than the yammy 150s.

[gofishin]

...Some recent performance figures in glassy conditions, which from other trip stats, counteracted the reduced crew weight anyway as she was sticking to the glassy calm water a bit [emoji1].

These figures were with just me on board, only 15 hrs up on the donks, ~250L fuel & ~120L water, ~ 125kg gear. On other days with 4 or 5 adults and a lot more weight/liquids, the figures at 25 – 30kn don’t change much from below even in 15-20kn Moreton Bay conditions – at least from what I have seen anyway.

All the readings below were from the gauges except for the last column [km/h], which I calculated as I didn’t write them down. Fuel data is the combined Total for BOTH donks.

rpm, kn, L/nm, km/L, L/h, [km/h calculated]
3000, 15, 1.8, 1.0, 26.4, [28]
3200, 18, 1.5, 1.2, 28.6, [33]
3400, 20, 1.5, 1.2, 31.2, [37]
3600, 22, 1.5, 1.2, 33.8, [41]
3800, 24, 1.6, 1.1, 38.6, [44]
4000, 25, 1.6, 1.1, 42.8, [46]
4200, 26, 1.8, 1.0, 47.2, [48]
4400, 27, 1.8, 1.0, 49.0, [50]
4600, 29, 1.8, 1.0, 54.7, [54]
4800, 31/2, 1.8/1.9, 1.0, 60.4, [57]


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Just to update above...
I have since changed to 3x16x21.5 Zuke Watergrip props, and the consumption & economy shown on the gauges is even better.

However, I have also confirmed, via two calibration checks over ~1500 litres thru the donks, that the figures aren’t quite so good! Economy figures are about 7% worse than above figures (which were with 3x16x20 props).

With the 21.5 props I now regularly see 1.6-1.8L/nm “on the gauges” between 25-28kn, with ~10kn wind and a good load. However, 7% worse are the real economy figures.

Still bloody good for just over 3t empty, just not ‘phenomenal’ [emoji6]
Cheers


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