New prop - bad trim

[petterg]

I guys.
I've come to this forum hoping for some help to find a propeller type the will fit my boat. I've found the right size, but I can't get the bow to lift, so I need a different shape, same size. Here is the story:

I bought a used Castello 533HT with an Evinrude e-tec 60hp. It was setup with an 15in pitch alu pro and was running quite bad - engine hit rev-limiter and water was hitting high on the engine and splashing into the boat!
The boat is 17.5 feet, 560kg
http://www.castelloboats.fi/en/533ht...specifications

The hull starts as a V-shape, but the rear 2-3 feet is like a catamaran, kind of like a W-shape. There is no gradually change from V to W. The bottom of the V just stops. Hence there is quite a distance from the end of the center part of the hull to the engine.

The first thing I did was to mount the engine 6cm (2.3in) higher. That made the boat behave a lot better. Water did no longer slash into the boat after hitting the engine. The alu prop had no issues regarding grip/ventilation/cavitation/trim after this. I was considering mounting the engine even higher.

Then I got an 21in SS prop - Solas New Saturn. (After testing smaller pitch sizes of the same prop.) Now my WOT was acceptable - a tiny bit on the low side, but I could not use the trim! My bow was plowing the water. Just a tiny bit of trimming the engine out and the prop lost grip. I believed that if could just get the bow to lift my WOT would be perfect.

So I mounted the engine down. This allowed me to use most the trim range, but the bow still will not lift!

What I wasn't aware of was that this prop has quite a bit of trailing edge cupping. Reading about propellers I learned that trailing edge cupping lifts the stern. I believe that is my problem. I need a prop that will make my bow lift, without changing the engine rpm.

The Solas dealer where I bought the prop say they don't have any better fit prop than the one I have, so I will return it and get my money back. The props they have with higher rake does not fit the 60hp e-tec.

I know a 21 pitch on a 60hp e-tec sounds too much, but this boat really is build for going fast with small engines.

To my surprise prop manufactures are very restrictive with data about their props. I just can't find any telling how much cupping or rake their prop has. Can anyone help to suggest a type of prop that will allow me the get the bow lifted, keeping rpm about the same, and hopefully increase top speed?

 

[steelespike]

If the boat is plowing I would check the hull for a distortion of the bottom. Put a 3 or 4 ft.straight edge along the keel from the transom forward.
Check for a hollow ahead of the transom.Or any distortion. Impropper storage and or trailering can cause hull problems.
​ Perhaps a manufacturing deffect.
From the pictures of the 533 it runs bow high perfectly with an etec that is obviously trimmed up.
Talk to Castello about the appropriate prop.There is a contact tab in the site you posted.
The Etec 40,50 and 60 use the same prop series.They are identical but for the hp.
Here at iboats there are 9 al. props listed including one 4 blade,
there are 9 ss props with three 4 blades.Hard to believe there isn't a one to suit your boat.

 

[petterg]

Thanks, Steelespike

The keel seems pretty straight using my 4.5 feet steel bar. Also the sides of the keel. The fact that trimming is fine when using the 15p alu prop also indicates this is not an issue with the hull. With the alu prop and engine mounted high felt like what you see in the picture. Only problem was the engine hitting rev-limiter.

Yes, I'm sure there is one propeller that will fit. But I wonder which one. The information given for each one doesn't give me enough information to choose between them. There is no information available that makes me think one is better suited for my needs than any other. I need help to narrow the selection of props down to a couple of options to try. Which one will give more lift to the bow than the Solas? I can rule out Solas New Saturn and Solas Rubex NS3 (as they have the same blades, different hub. I've tried them both).
So, knowing that the Solas props does not provide the bow lift I need. Which ones will provide more bow lift?

 

[steelespike]

Props with more "rake" provide more bow lift.The Merc. Laser II Is said to provide more bow lift.
According to some a 4 blade provides hole shot (stern lift) and Bow lift at speed.
Hustler has a 4 blade.The Solas HR Titan in 3 or 4 blade said to work well.
I'm pretty sure you should start with a 17" Brp al prop if the 15 brp works a 17 should
work at the right rpm.I think at least part of your problem is the motor can't reach wot rpm with a 21".
Once you find the rpm with the 17 you can fine tune pitch and design.

 

[SkiDad]

I would look at a 17 pitch turning point hustler. I can vouch it lifts the bow. Well at least on my boat it did. A 17 TP will turn the rpm of a 19

 

[petterg]

Does more rake decrease engine rpm similar to what trailing edge cupping does?

According to Mercury Prop Selector the Laser II does not fit on my 60hp e-tec.
Solas H(igh)R(ake) series does not fit either.

 

[petterg]

Does the Turning point Props have an excessive trailing edge cupping (in order for a 17p to give the rpm of a 19p I'd guess the factor must be cupping). The issue with the prop I have is too much trailing edge cupping (and/or too little rake). Then I'm afraid this prop may be a step in the opposite direction.

 

[steelespike]

What was the rpm and wot gps speed when bumping the rev limit?
Solas Titan Is described "A performance prop for high speed planing hulls.High rake provides excellent bow lift".
This came from a Solas list of props for Etec motors.

 

[petterg]

Sadly the Titan stops at 19pitch. I think I need a 21p, unless rake decreases WOT rpm significantly. Will it?
Also it is said to be designed for heavy loads with increased blade area. My boat is surely not a heavy load. Titan HR3 could have been something, but it doesn't come with the 13tooth hub.

Rev-limiter is about 6200-6250. Recommended rpm is 5500-6000 for this engine. Gear ratio is 2.67.
GPS speed with 15P alu was 24.2knots (average of driving in multiple directions to compensate for wind and seacurrents). Before mounting the engine up I had an unreliable reading of about 23knots (I tested this only once, near a river).
The 17P SS New Saturn gave 28.2 knots at rev-limiter, high mounted engine, and not able to trim much out.
The 19P Rubex NS3 I didn't test much - tacho showed 6100-6150.
The 21P Rubex NS3, gave 29.4knots with high mounted engine, and not able to trim much out. Tacho showed 5800-5850 light loaded. With full family and some some extra load I got 5500-5550. Family didn't like going fast on bumpy sea, so I didn't get a reliable speed reading with them on board.
When I mounted the engine one hole down I got to use almost the full trim range, and speed reading was 29.5knots and tacho showed in the same range. Trim was significantly more out in this test than in the first test with 21P.

Slipp is pretty high. It increased significantly from 17P to 21P. I believe this is because of the stern being lifted too much - and the larger the prop, the more the stern lift effect of the trailing edge cupping. Also, my first reaction to the 21P was that it felt heavy to get the boat out of the hole. But by the next acceleration it didn't feel heavy. Then I figured I was inpatient with the first test - the engine was still cold. Warm engine does not feel slow accelerating.

Trim all the way in reduces rpm by 300. Then speed drops by 1.8knots. If I trim out from my top speed test trim, just by one very short click on the button, the prop loses grip and the rpm's hits the rev-limiter. Grip is also easily lost in turns if I don't trim in.

I believe that a correct lift to the bow will decrease the hull drag and correspond to an increase of rpm by 200. I also believe that a prop that provides such lift will have less slipp, hence make the boat feel heavier to the engine and thereby decrease rpms by about the same.

I emailed Solas several days ago asking for cupping/rake/area of the New Saturn. They have not yet replied.

 

[steelespike]

List of Solas props for Etec 60. Titan "Performance prop for High speed planning hulls".
" High rake blade design provides Excellent bow lift".
" Excellent acceleration & top speed,cupped blade design increases bite & reduces slip".
No indication for heavier boats.
I think there is a reason only a 19" is the max.available.I would call the Titan a aggressive prop.
I find it unusual that a 21" prop is so close to over revving. 5850 at 29.4K 33.8 mph indicates 22% slip.
Normal slip is about 10 or 12 % Excessive trim ? might do that or a poor setup.
Don't assume that the tach is accurate just because its relatively new.Maybe they can plug in a tester.
The 533HT is said to do 28 K with a 50 hp.If we calculate for pitch using 32 mph,2.67,6000, 12% slip
we get about a 17" pitch.

 

[petterg]

I now notice there are there are multiple descriptions that differ for the Titan. Even Solas website and Solas prop catalog differ in their description of Titan. The website say: "High camber blade and large blade area design" and "Great load carrying capability" - to me that sounds like a prop for heavy load, not speed - which match what the dealer say. While the Solas prop catalog description of the Titan sounds more like how the website describes their HR3. I'm even more confused now than before!

I think my high slip indicates that the prop is too high in the water. I blame the stern lift effect of that. This because slip with 15P alu was 13% with engine mounted high and nice trim. I will not believe that all the 17P, 19P and 21P should require to mount the engine more than one hole down. If it is a poor setup, I would think at least I should be able to get somewhat similar behavior with 17P NS and 15P alu at 23-24 knots. As I didn't, I'd like to blame the prop. Behavior with the other props were quite similar to each other.

Maybe you're right that the Titan will reduce slip enough to compensate for 2in less pitch.
I've found one site where New Saturn and Titan is compared: http://www.rib.net/forum/f36/propeller-test-programe-5060-2.html#post53546
As it happens, this posting also is 21P NS vs 19P Titan. Result being Titan give significantly less speed, more rpm and has more slip than NS.
I'll try to send a mail to Solas once more asking about NS vs Titan.

 

[steelespike]

Seems that the best source for prop selection would be Castello.
While the tests may give some results prop to prop. I think those model props on a 533HT might be completely different.
Especially when comparing motors up to 300 hp on completely different hulls

 

[petterg]

I know that forum post has a low value as test results. Still, it's the only I've found where Titan and NS are tested on the same boat/engine.
I've sent a mail to Castello asking if they have a recommendation. Hopefully they are more willing than Solas to reply to their customers.

Thanks for all your input, Steelspike. I'll update whenever I get any new information.

 

[steelespike]

It's very likely that after all your research your first prop selection will end up a starting point.
It occurs to me that your original 15" prop worked well but for recessive rpm.It would seem a good prop shop could asdd pitch or cup
to enhance your results both for best speed and correct rpm.
Or the same prop in a 17. To get a starting point that functions normally.
I'm still suspect of the 21" prop Close to over revving. Barely within wot rpm.
If you look up Etec 60 performance reports on their site you'll find prop sizes 15" and 17" pitch but for the pontoon boats.
The boats aren't a good match for your boat but certainly more accurate than the 150 to 300 hp prop tests.
Often if a prop is too much for the application slip will tend to be high.
I can't speak to the Etec electronics but I sure would like to see the rpm by an outside source.

 

[steelespike]

Did a little more Etec tests. 8 boats about the same size and dry weight.
Glastron GT 160 1900 lbs 15" ss prop 6000 @ 29.4",Triumph 1700 1400 dw, 17'4", 15" @ 5575 29.1,Beavertail, 17'6" 550 dw,17" @ 34.8,
Stratos 176XT 17'6"(bass) 1200 17"al 5620 @33.8,Same boat with a 15" al/c 5850 30.9, Twin V 16'10"850dw, 15ss @ 5725 30.3.
Point is these boats with widely ranging weights and design none are close to a 21" pitch. yet speeds are all around that of the
the Castello with a 50 and 28K.(32mph)

 

[petterg]

I wasn't aware that evinrude had such performance reports.
Interesting reading. Most of those boats seems to be more stern heavy than the Castello. Glastron seems to be the most comparable in regards to weigth distribution. But the boat is way heavier than the Castello. Glastron get about the same speed as I with the 15p alu, but I had more rpms.
I also notice that the 32+ mph test results are using the Viper prop.

And a quote that makes the report extra interesting
Glastron: "Propeller: BRP Aluminium(TM) Material: Stainless Steel" (Partnumber resolves to alu)

The engine sound changes significantly when it hits the rev-limiter. I trust the sound more than I trust the tacho. And when moving the throttle in the upper 10% of it's range doesn't change neither sound, speed nor rpm, this also confirms that it has hit the rev-limiter. (With the 21p there is a significant change in speed, sound and rpm when moving the throttle in the same range.) So I'm 100% sure I hit the rev-limiter with 15p alu and 17p New Saturn. One may claim my engine was mounted too high, but the water above the plate indicates it's mounted too low. Rev-limiter is said to be 6250, so that is my reference for the tacho.

 

[petterg]

The mystery of the different descriptions of Titan is solved. In the props catalog Solas put the description of H(igh)R(ake)3 for both the Titan and the HR3. While on the website Titan has got its own description. As the HR3 has the same description both places, I believe the correct description of the Titan is the one on their website.

 

[petterg]

Here's the reply from Solas:
----------------
Usually, we would recommend the propeller with bigger diameter for higher gear ratio engine like yours. Our current Titan is with similar diameter like the 21p. If aluminum propeller is still acceptable for you, maybe you can try 9411-139-19. Or, we also have 4 blade RUBEX HR4 9453-130-21 for your reference.

As the blade shapes between NS3 and Titan are different, it’s difficult to just compare the cupping and rake. The blade area of NS is bigger than Titan but there are also positive feedbacks for D series Titan on Evinrude engines.
We will still recommend you to check with our local dealers because they can make a more appropriate suggestion with reference to your actual boating condition there.
-----------------

They did not comment on the descriptions mixed up for Titan and HR3 in the prop-catalog.

Does it make sense to prefer a larger diameter for a light weight boat, just because of the engine gear? I though gear was dictating pitch, and higher pitch tend to have smaller diameter. Their statement of diameter did not make sense to me.

(Castello has not replied)

 

[steelespike]

At 2.67 the prop is turning slow compared to say 1.83 for 2.00. Doesn't lend itself to speed; simply because it will never turn as much prop rpm as a 1.83 or 2.00.
But it will pull just about anything even if nailed down. A natural on a pontoon or other hard to push boat.The Merc 60 has a 1.64 ratio so prop speed can be much higher the prop needs to be smaller and pitch comparatively lower for similar applications.A little apples and oranges but I think its clear that 5500 will turn a prop a lot faster at 1.64 ratio.

 

[petterg]

I'm thinking of pitch as wheel size on a bike. Wouldn't a high pitch prop spinning slowly give the same speed as a low pitched prop spinning fast?