Props and Fuel Economy

[Darren Mc]

Hi all,I have a 150 hpdi 2 Stroke with which i can only get 4850rpm at wot. Should be between 4850rpm - 5850rpm. Running a 4 blade cyclone prop 14 1/8 x 19 and do go offshore min 130klm round trip each time. Getting pretty ordinary fuel economy at present. Will i improve that by coming down to a 14 1/8 x 17 4 blade? Also will that change drop my top end? Thanks for any info

[UNCLE NUGGY]

Darren
sounds like your running in 5th gear going uphill.
had a 19pitch on a 115hp 5.6 aly boat , wasnt gettin full noise,changed to 17 & was in wot rec range.it was quicker with the 17 pitch. now i have small tinnies that are always powered to max recommened or more .
cheers
UN

[trueblue]

You need to gain 1000 rpm, and a 2" reduction of pitch to 17" P should only give you approximately 5 to 600 rpm extra if keeping the same diameter of prop which is not enough in itself.

It sounds like you have way too much pitch and might even need to come back to a 15 P, but also might need to reduce prop diameter as well.

Post some photos of the motor set up - trim the motor to be neutral (square to the bottom of the hull and take a photo at 90 degrees to the motor with the camera at the same height as the bottom of the hull. we need to see the height of the anti cav. / vent. plate relative to the bottom of the hull before anything else.

At what trim is your WOT revs of 4850 (ie neutral trim, trimmed in, trimmed out a little, trimmed out to the max before it breaks loose...)

need more info

cheers

Mick

[trueblue]

4 blader will be thirstier than a 3 blade prop unless perfectly tuned to your boat...

[Jabba_]

Optimum running range for a 150 E-tec is 5300-5500rpm, and you want to be toward the top end off this scale... Reducing you pitch 2 inches will nett an increase in your RPM's by 600, giving you a WOT off 5450rpm. Perfect.

You will also improve your economy and lift your top speed, and increase the life span off your motor, because your motor is not labouring.

[Scalem]

Darren,

The symtoms you describe are exactly what I am going through at the moment with my Jonno 2s 70hp. I can't offer any more advice than what Mick has given, I think he is on the money.

I won a $500.00 gift voucher with Solas Propeller Warehouse, the drive to see them on the Sunshine coast was worth it and I am now the proud owner of a stainless prop which has smaller blades to the original, but same pitch. The best option was to go a 15P, but they wanted $695.00 for a new one, so I took this demo prop instead. I would be testing it this weekend except for the weather, so I will have to wait. I found the guys extreemly helpful. Talk to Shane Evans 0754379400.

Scalem

[Alan_L]

Darren

I had the same problem on my 150 2 stroke, originally had a 17 X 14 3/4 SST prop, but could only get 5150 rpm at WOT, changed to a 15" Rebel prop and rpm increased to 5350 and fuel economy increased from 1.4km/l to 1.6 km/l at cruise. Engine sounds sweeter, quicker response, and I didn't loose any top end speed.


Alan

[TimiBoy]

I dropped an inch in pitch and 3/4 inch in diameter by replacing the Mirage prop my 250 Verado came with with an Enertia.

Put an extra 400 rpm on at WOT, with slightly lower fuel usage and 4 extra knots top speed. Cruise is significantly better, with improved economy.

Holeshot I can't tell because even on the old prop she threw herself out of the water.

[FNQCairns]

4 blader will be thirstier than a 3 blade prop unless perfectly tuned to your boat...

This is true, find yourself a 3 blade that works rather than the 17p you mentioned although it will be better, it's pretty bad atm (fuel economy might be close or slightly better also). Don't know what your boat is but if it fits the rec fishing bell curve for weight/design and doesn't out lie to either side odds are whichever 4 blade you choose will have you paying interest on the purchase forever in comparison:'(

cheers fnq

[honda900]

Darren Mc,

Bill Corten's cruise craft 625 outsider had a 150 hpdi, I remember him telling me that he changed the prop to a 3 blade Yammie 4 stroke prop to sort his boat out, he uses that boat for his bar crossing courses and fuel economy and performance were very good. Check out bushnbeach he usually posts his email address, I am sure he would be happy to tell you what he runs.


Regards
HOnda

[chop duster]

Timiboy,
What pitch enertia are you running, we are running an 18, down from a 19 mirage. Those mirages are OK at cruise but crap for topend or even fast cruise.
Darren,
What sort of boat are we talking about here, more details will help, and yer, a transom piccy will help rule out some problems.

[TimiBoy]

It's an Enertia 16", 14 3/4" diameter. Had a 17" Mirage.

[Darren Mc]

Hello all,According to the motor manual wot rpm range is 4850-5850 rpm and they say middle of that range is what is best. So the desired rpm would be about 5350rpm. The boat is a 6m fibreglass half cabin Reef Raider. The 4850rpm i got was with the motor trimmed right up at maximum before it breaks loose. Mind you that was still doing 77km/hr which felt pretty quick i must admit.I had a look at the motor height on transom and the anti cav plate, when level with the bottom of the hull sits about 5mm higher than the bottom of the hull.Just a little more info : I did 128km's and used about 110ltr's fuel. Not very impressed...

[trueblue]

how far back from the bottom of the transom is the prop?

You might be able to lift the motor one inch which will give you about 250 rpm straight away. water will rise up about 1 " per foot that the prop is behind the transom.

raise the motor plus a little tuning on the 19" might do what you want for rpm especially if the diameter is reduced a little

cheers

Mick

[Darren Mc]

Prop is about 65cm back from transom

[trueblue]

You should then be able to lift the motor one hole regardless of what prop you choose and still have lots of trim and water around the prop.

That should give you 51 to 5200 rpm, and that will improve fuel economy a little by having less drag.

Then you just have to decide what wot rpm you are going to go for before you think more about props.

At 5350 being in the middle of the rev range you don't need much more rpm's.

I was always taught though to shoot for wot rpm's to be in the top quarter of the recommended rev range, rather than half way like at 5350. You will have to consult with your engine manufacturer about that though because i am not familiar with that engines recommendations. But for fuel economy you don't want the engine to be lugging at lower rpm's.

If you set your mind on 5350 rpm, and you want to keep your 4 blade current prop, then after raising the motor, see if you can get the prop detuned a little by a professional by grinding the back of the blades to be thinner and by reducing the diameter a little.

or, changing to a 3 blade prop in a different brand but still 19" you might hit the nail on the head.

Alternatively if you want to shoot for the top 1/4 of the recommended rev range at 5600 rpm, you will need to play with 17" pitch props.

You also need to load the boat up to a fairly typical full load when testing your prop.

cheers

Mick

[devendiva]

I am in the same situation at the moment. On a Haines Hunter 600 Classic with 175 Etec I was getting 5050 RPM at WOT trimmed to almost breaking loose. This was with a 14 3/4 x 17" Viper. I raised engine height one hole and gained not a single RPM.

BRP sent me a Viper 15 x 14" and a 15 3/4 x 15" Rebel to try. I tried the 14" Viper last weekend. It was terrible. The RPM increased to around 6100 and I lost about 5 knots top speed. It sounded shocking too - revving and getting nowhere. I didn't stay at 6100 RPM very long. I was under the impression that RPM should have increased about 200 for each inch reduction in pitch, so at a 3" drop in pith, I was expecting about 5650 RPM, or maybe a little less as its gone up in diameter slightly, but it was much higher than this.

I only had a very brief go at the Rebel as I ran out of time / tide. It saw about 5300 RPM at WOT and top speed was about the same as the 17" Viper. I'm planning to give it a good run this weekend to see how my economy is at cruising speeds. I don't think they make a smaller pitch Rebel. If I had my time again, I'd definitely go as close to the the max HP on this hull - 230 HP. At 35 knots it feels so slow.

[FNQCairns]

I am in the same situation at the moment. On a Haines Hunter 600 Classic with 175 Etec I was getting 5050 RPM at WOT trimmed to almost breaking loose. This was with a 14 3/4 x 17" Viper. I raised engine height one hole and gained not a single RPM.

BRP sent me a Viper 15 x 14" and a 15 3/4 x 15" Rebel to try. I tried the 14" Viper last weekend. It was terrible. The RPM increased to around 6100 and I lost about 5 knots top speed. It sounded shocking too - revving and getting nowhere. I didn't stay at 6100 RPM very long. I was under the impression that RPM should have increased about 200 for each inch reduction in pitch, so at a 3" drop in pith, I was expecting about 5650 RPM, or maybe a little less as its gone up in diameter slightly, but it was much higher than this.

I only had a very brief go at the Rebel as I ran out of time / tide. It saw about 5300 RPM at WOT and top speed was about the same as the 17" Viper. I'm planning to give it a good run this weekend to see how my economy is at cruising speeds. I don't think they make a smaller pitch Rebel. If I had my time again, I'd definitely go as close to the the max HP on this hull - 230 HP. At 35 knots it feels so slow.

Mate you are lost! what would they send you a 14p or 15p prop for sheesh! did you talk to a kid on work experience for a day?? Ask for a postage refund!!

IMO Stick to 17p at this stage and find a 3 blade prop any model name it will not matter as long as it fits but here is the kicker make sure it has less diameter, try and make 14inch diameter the absolute low end but keep a death grip on the 17p portion of the prop specs until testing proves otherwise (you may be able to run a small diameter 19p).

Does BRP have a 14.25 or a 14 3/8 x 17 3 blade in their lineup any model except 4 blade? if so test it ...will make you smile in comparison to now although it may be the first step not the last step toward getting it all working well on the water.

cheers fnq

[devendiva]

FNQCairns,

I have actually been speaking directly to Paul Armstrong who I believe is one of the BRP/Etec technical gurus. What is your reasoning for sticking with the 17" pitch at all costs?

I have almost given up on it and am ready to just use it as it is and forget about the whole props / RPM thing.

Will I really see a real benefit that will make the effort worthwhile? Where will I see the benefit? Top speed / fuel economy?

Just looking for some inspiration to keep fighting on.

Thanks

[Outsider1]

Hi devendiva,

these threads on the E-Tec Owners Group site might help;

RPM Range guide for 2008 E-Tecs

http://forums.etecownersgroup.com/tool/post/barnaclebill/vpost?id=2671224

Propping for a 175 E-Tec on a 21ft Cuddy

http://forums.etecownersgroup.com/tool/post/barnaclebill/vpost?id=2738127

Cheers

Dave

[Reel Blue]

Devindiva,
I have 175 etec on 650 Classic and have had the same issues as you. I have tried several props and the one I have settled on is a BRP stainless 15X15 prop. This prop reaches 5700 lightly loaded and 34 knots. Hole shot and acceleration is impressive and it pushes alot of weight easily. Top end speed is down a little on the 14.74 X17 viper, but with my current prop the boat feels more well balanced and agile offshore, which is my preference. Fuel economy at cruising speeds is also improved.

[FNQCairns]

FNQCairns,

I have actually been speaking directly to Paul Armstrong who I believe is one of the BRP/Etec technical gurus. What is your reasoning for sticking with the 17" pitch at all costs?

I have almost given up on it and am ready to just use it as it is and forget about the whole props / RPM thing.

Will I really see a real benefit that will make the effort worthwhile? Where will I see the benefit? Top speed / fuel economy?

Just looking for some inspiration to keep fighting on.

Thanks

Sorry missed your reply till now, the 17p portion is the spec that shoots you, if you stick to 17p by the numbers you have given above you will hold onto your good cruising speed at good RPMs and you will have a nice reserve of speed left to blast outside or home on those glassed out days and all this with up to 20% better economy than those advised props!

The only way to hold onto these good things and increase revs is to decrease diameter, sell peter to pay paul.

Going down in pitch seriously compromises the boats performance in these areas, most props are sold with enough diameter for pitch to tow a barge, your boat WILL come alive if you find a prop to test as I outlined above -you may not be perfectly setup as setup is stepwise with each improving set of numbers but it will be a better boat than decreasing pitch will ever give, a 15p is entirely a ridiculous proposition for your boat.

If you cannot source a 17p and are forced to step down 15p is way too far, 16p is a shame that will cost you money and perfromance but will work ok as ok goes, again testing will tell all.

cheers fnq

[devendiva]

Reel Blue, which BRP 15x15 prop are you using? Viper, Rebel or something else?

FNQCairns, If I need to stay with 17" pitch, is it possible (and economical) to have my current prop modified to reduce the diameter. I would think that a competent prop repair joint should be able to machine the diameter down a bit but is this viable?

Thanks

[devendiva]

I was just reading some of the posts on the etec owners group forum supplied by Outsider1. Plenty of posts about propping / RPM issues. Are Etecs particularly sensitive to propping?

In one of the threads, the guy went from a Viper to a Cyclone 4 blade and was thrilled with the results. Is this asn option? What are the pros and cons of a 4 blade

[FNQCairns]

Yes certainly possible to get the prop redesigned for extra revs although they can come back pretty rough depending, specifying it to stay pretty is costly. You could ask for no cup and and aggressive 'tipping' to gain an acceptable end result it may take a few returns for more work, going too far can wreck a prop or make it more costly again to get it back to where it last was.

I have a SS 17p marked out to do this to ATM in the backyard want the efficiency of travel per revolution but want to decrease resistance to turning enough to accomplish my chosen WOT rpm, on my engine I cannot run a standard 15p prop but can run most 14s, you have the advantage in that you can easily run a standard 15p blade, to date I have not found a standard prop that tick all the boxs on my boat so I have to spend the time to modify every one, I don't care about how it looks only how it performs. Don't forget as advised by someone above you may still be able to raise you engine to help gather the end result.

But if you have access to trial props best to use that first.

4 blades are a little like square wheels on cars, how square your wheels are before fitting the 4 blade will be proportional to how happy you are with it. If you have a working Ok 3 blade fitted, a 4 blade will need to be very well tuned to match it in performance across the entire operating range and it's hard enough finding a 3 blade off the shelf that works well on fishing boats, the physical inefficiency of any extra blade makes it almost impossible.

No e-tec are not, it's all just drama, any prop will work well, the prop couldn't care less what shaft rotates it, zuks differ a little though. pretty much if someone finds a prop that work well on their e-tec it will work well on someone eleses yamaha and the converse applies, we are talking fishing boats with big weight and huge planing wetted lengths.

cheers fnq

[Malcolm W]

FNQ,
My 115 2 stroke yamaha had a 3 blader ( on 5.6 alutech CC ) and broke loose at the sligtest turn or trim out. I played with the height and had no luck. The motor was set up qiute deep seemingly to compensate for this ( 25mm below the keel ) Solas sent me the same size 4 blader and it gripped heaps better but the revs were down 2-300. I was able to raise the motor 3 notches and still not break loose as mutch as the yamie 3 blader. The end result was I settled on 2 notches higher as max rpm was approx the same ( 5300 ) as the 3 blade but 25 knots @4000 as opposed to 21 knots @ 4000 with the 3 blade. So far fuel economy is better. It sounds like I should have tried some other 3 blade options but the solas rep seemed to push the 4 blade prop for my motor. He also recommended the 115 4 stroke only should use a 3 blade prop. Do you think 4 blades take a lot more to set up and did I just get lucky with mine.

Cheers Mal.

[FNQCairns]

FNQ,
My 115 2 stroke yamaha had a 3 blader ( on 5.6 alutech CC ) and broke loose at the sligtest turn or trim out. I played with the height and had no luck. The motor was set up qiute deep seemingly to compensate for this ( 25mm below the keel ) Solas sent me the same size 4 blader and it gripped heaps better but the revs were down 2-300. I was able to raise the motor 3 notches and still not break loose as mutch as the yamie 3 blader. The end result was I settled on 2 notches higher as max rpm was approx the same ( 5300 ) as the 3 blade but 25 knots @4000 as opposed to 21 knots @ 4000 with the 3 blade. So far fuel economy is better. It sounds like I should have tried some other 3 blade options but the solas rep seemed to push the 4 blade prop for my motor. He also recommended the 115 4 stroke only should use a 3 blade prop. Do you think 4 blades take a lot more to set up and did I just get lucky with mine.

Cheers Mal.

I think you did a good job of working around the 4 blade to get an acceptable result based soley on your 4 blade numbers, I have no idea why in your instance the 3 blade wouldn't work, the numbers you gave are akin to the performance expected if one of the blades was missing assuming they were both the same pitch although the 4 blade is working like a 18 or 19p and the 3 was like a 15p...what were they really? and how well do you trust the numbers you gave?

But regardless if there is no outlying reason individual to that hull that cannot be got around (like your aeration problem) some further testing of 3 blades may see you yet doing better again although you may need to come down a hole 4 blades will run higher than 3 blades, a prop that blows out is a prop that blows out and if considered unacceptable, it is unacceptable!.
Interested to hear if you have a foil fitted, they will severely restrict efficiency until raised very high, would only be a part of the overall though.

Overall not enough info to determine (guess)what might have been up in your instance.

cheers fnq

[Malcolm W]

I think you did a good job of working around the 4 blade to get an acceptable result based soley on your 4 blade numbers, I have no idea why in your instance the 3 blade wouldn't work, the numbers you gave are akin to the performance expected if one of the blades was missing assuming they were both the same pitch although the 4 blade is working like a 18 or 19p and the 3 was like a 15p...what were they really? and how well do you trust the numbers you gave?

But regardless if there is no outlying reason individual to that hull that cannot be got around (like your aeration problem) some further testing of 3 blades may see you yet doing better again although you may need to come down a hole 4 blades will run higher than 3 blades, a prop that blows out is a prop that blows out and if considered unacceptable, it is unacceptable!.
Interested to hear if you have a foil fitted, they will severely restrict efficiency until raised very high, would only be a part of the overall though.

Overall not enough info to determine (guess)what might have been up in your instance.

cheers fnq
FNQ, thanks for the reply, No foil fitted and the yamie 3 blade is only 80hs old and in good condition. I trusted the solas rep as he said Yamaha props are common to let go. I trust the results as I am fusssy about the boats performance and my tests were identical on a flat estuary. I have had other issues with the hull / motor performance and I am starting to think this is contributing. The hull has large reverse chines and deep V ( for this size ali ) which contributes to the cavitation problem when turning. Anyway the upside is a good result but at a cost ( $750 ) PS both props 13x 17

[Reel Blue]

I was told by Steve from Solas that Etecs are are little different than other brands to prop as the torque curve delivers more power early on and less approaching WOT. This makes it more difficult to achieve higher RPM at WOT with a prop that would traditionally be suitable for that size motor. This does appear to match my experience and the experience of others.

The 15X15 stainless prop I have came in a BRP box but is unnamed.

I do agree that a 14x17 prop would be worth trying and could be a better choice that what I have. However it is not available from BRP as far as I know and I was never offered one to try. I was not happy having to puchase another prop for around $700 from solas.

My dealer and BRP believe the prop I have now is the most suitable.