4 Way Aluminium Prop Test

[trendsetter240]

I've been trying out a few props as this season I have repowered my boat. This motor is a different HP and gear ratio from my last so it has taken some trial and error. I still don't think I have found the perfect prop but here are the results of my test.

Boat:
1969 Slickcraft SS170V, 17ft, 1100lbs dry, motor 237lbs, 1 passenger 220lbs, 6.6 Gallons of fuel, tools and safety equipment 50lbs. Deep V 17 degrees of deadrise, max 100HP.

Motor:
1995 Evinrude ELEO 70HP. Completely rebuilt and running excellent. 40hrs since rebuild. Recommended WOT range 5000RPM to 6000RPM. Anti-ventilation plate 1.5 inches above bottom of hull and clearly visible when planing

Test Conditions:
At Sea level, appx 2 miles off shore, mild chop and slight tidal current. 10 degrees C. Tests were performed both with and against the current and the results were averaged between the two. Boat was refueled from a jerry can on another boat after each test. Speed measured with Garmin GPS, RPM with new Teleflex tach.

Prop #1: Solas Amita 13.25X13p 4 blade.
Prop #2: BRP 13.5X15p Alum. 3 Blade.
Prop #3: OMC 14X17 Alum. 3 blade
Prop #4: Turning Point Hustler H2-1317 13.25X17 Alum. 3 blade


Prop #1: Solas Amita 13.25X13p 4 blade.
Pitch Gear Ratio RPM MPH
13 2.41 3500 13.5
13 2.41 4000 16.4
13 2.41 4500 20.1
13 2.41 5000 23.8
13 2.41 5500 25.8
13 2.41 6000 28.3
13 2.41 6600 33.7

Prop #2: BRP 13.5X15p Alum. 3 Blade.
Pitch Gear Ratio RPM MPH
15 2.41 3500 18.4
15 2.41 4000 25.2
15 2.41 4500 28.0
15 2.41 5000 31.6
15 2.41 5500 34.5
15 2.41 5800 36.5

Prop #3: OMC 14X17 Alum. 3 blade
Pitch Gear Ratio RPM MPH
17 2.41 3500 20.1
17 2.41 4000 23.6
17 2.41 4500 28.6
17 2.41 5000 31.9
17 2.41 5500 34.4
17 2.41 5600 35.8

Prop #4: Turning Point Hustler H2-1317 13.25X17 Alum. 3 blade
Pitch Gear Ratio RPM MPH
17 2.41 3500 17.5
17 2.41 4000 25.9
17 2.41 4500 29.7
17 2.41 5000 34.2
17 2.41 5300 36.5

At the moment I have decided to keep the BRP 15p and the Solas 13p. The BRP is a good all around prop which allows me to reach good RPMs and a decent speed. The Solas will be good for heavy load situations or water sports.

I think my next step will be to look at SS props and see where that takes me. Hope this info helps out someone looking at purchasing a new prop.

Comments, questions, concerns, charts, opinions..please post away .

 

[sleeper]

Re: 4 Way Aluminium Prop Test

It looks like the TP hustler is the most efficient prop, but you need a 15 pitch in it instead of 17 to bring the rpm up.

 

[hwsiii]

Re: 4 Way Aluminium Prop Test

Trend will you please take me a picture of the stern of the boat at the transom and elevation height about even with the anti ventilation plate, but with the motor tilted up, so I can see the true hull form of your boat.



H

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

Trend will you please take me a picture of the stern of the boat at the transom and elevation height about even with the anti ventilation plate, but with the motor tilted up, so I can see the true hull form of your boat.



H

H, I would love to but my boat is at it's slip in the water for the season already. I will see what pics I can find of the hull for you and post back.

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

Here are some pics of the boat coming out of the water after last season. The motor in the pics is NOT the motor used for this test.

http://i764.photobucket.com/albums/...craft SS170V built by Grew Boats/IMG_3986.jpg

http://i764.photobucket.com/albums/...craft SS170V built by Grew Boats/IMG_3985.jpg

http://i764.photobucket.com/albums/...craft SS170V built by Grew Boats/IMG_3982.jpg

http://i764.photobucket.com/albums/...craft SS170V built by Grew Boats/IMG_3980.jpg

 

[bob johnson]

Re: 4 Way Aluminium Prop Test

I bet you would get more than 38 mph if you went with a SS prop.. 15 or 16 or 17 pitch.

the turning point with a lower pitch also seems to be a big possibility...to get you lots more speed....

bob

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

I bet you would get more than 38 mph if you went with a SS prop.. 15 or 16 or 17 pitch.

the turning point with a lower pitch also seems to be a big possibility...to get you lots more speed....

bob

Yeah, I'm going to think on it for awhile. I found a new prop shop in my area that I am going to check out on the weekend. If they have a trial program I will see what I can get with SS props.

I am also thinking about the TP in 15p or the Solas in 15p but I'm not convinced either will be significantly better than my current BRP 15p.

 

[180shabah]

Re: 4 Way Aluminium Prop Test

I am also thinking about the TP in 15p or the Solas in 15p but I'm not convinced either will be significantly better than my current BRP 15p.

Look at your numbers, the 17" TP is almost identical to the 15" BRP up untill WOT, where the speed is the same, but RPMs are lower. Dropping 2" on the TP Will bring your WOT numbers up and improve overall performance at lower RPMs.

Of course we are only looking at snapshots. You haven't told us anything about:
hole shot
minimum planing speed
ventilation in turns

And hwsii still needs info on your motor setup, you might still get more out of it.

 

[hwsiii]

Re: 4 Way Aluminium Prop Test

Trend, these numbers don't make any sense, but I have to assume that you wrote your numbers down right for your tests. So that means that either your Gear Ratio is wrong or your tach is wrong, normally I would say it is your tach, because they are notoriously known for being wrong. I think it would be a good idea to bring a mechanics tach with you next time you go, and check the gear ratio of your motor, I found your gear ratio to be 2.42:1, but that doesn't account for these numbers.

Here are the results for Prop Slip on your props, and these are NOT correct, as you should NOT be getting NEGATIVE prop slip for at least the two props that show that, but that is what my numbers show, and these are Aluminum props. Your Solas prop shows a prop slip of 0%, and that is not possible either.

If you will go back and compare these numbers to your old numbers you will see what I mean, I realize you had water in the boat, but that still does NOT account for NEGATIVE prop slip now.

Prop Slip

Speed

Effective Prop Pitch

These props act like they have more pitch than they do, the BRP 15" pitch shows an effective prop pitch of over 16" and the TP shows the pitch to be over 17" and that is NOT possible, for either one them, they are aluminum not SS.



H

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

Trend, these numbers don't make any sense, but I have to assume that you wrote your numbers down right for your tests. So that means that either your Gear Ratio is wrong or your tach is wrong, normally I would say it is your tach, because they are notoriously known for being wrong. I think it would be a good idea to bring a mechanics tach with you next time you go, and check the gear ratio of your motor, I found your gear ratio to be 2.42:1, but that doesn't account for these numbers.

Here are the results for Prop Slip on your props, and these are NOT correct, as you should NOT be getting NEGATIVE prop slip for at least the two props that show that, but that is what my numbers show, and these are Aluminum props. Your Solas prop shows a prop slip of 0%, and that is not possible either.

If you will go back and compare these numbers to your old numbers you will see what I mean, I realize you had water in the boat, but that still does NOT account for NEGATIVE prop slip now.

These props act like they have more pitch than they do, the BRP 15" pitch shows an effective prop pitch of over 16" and the TP shows the pitch to be over 17" and that is NOT possible, for either one them, they are aluminum not SS.


H

Hi H, yes I wrote the numbers down in a notebook as I was running the tests.

The gear ratio is 12:29 or 2.41:1. This is from the factory service manual.

The tach I bought new from west marine about 6 weeks ago and installed myself. It is set on 6p and wired correctly. It could be off, I will try and have it tested. Also it reads RPM in increments of 200 so I have to try and get the needle exactly between 400 and 600 to read 500 for example. It's possible that I am reading the RPM +/- 50rpm.


These props acted like they have more pitch than they do on my last test too. I thought that was because of the cupping?

Maybe these numbers are affected by the tidal currents more than I anticipated as well..Next time I will go 10 miles off shore

It could be that these number aren't scientifically exact but should at least represent a real world example of performance.

I'm going out on the boat again this afternoon so I will post back more results.

 

[180shabah]

Re: 4 Way Aluminium Prop Test

Currents can have a HUGE effect on speed numbers, next time do back to back runs in opposite directions and average the two numbers.

As it stands now, 2.14 makes more sense than 2.41.

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

Currents can have a HUGE effect on speed numbers, next time do back to back runs in opposite directions and average the two numbers.

As it stands now, 2.14 makes more sense than 2.41.

Yep, I know. as I mentioned in the first post under test conditions, I did one run with the current then one run against it and averaged the numbers from the two.

My service manual says 12:29 which is 2.41:1. Unless the gear box was replaced by the PO with something else...

 

[hwsiii]

Re: 4 Way Aluminium Prop Test

Trend, my only concern is that if your tachometer is reading low, you may be hurting your motor, and I do believe that is the problem, unless you are using a boat speedometer.

It could be that these number aren't scientifically exact but should at least represent a real world example of performance.

And I agree with you whole heatedly that these numbers are very representative of the real world and comparisons between the props.

My next question would be if these are GPS numbers.




H

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

H, yes the speed numbers were recorded using a Garmin 60cx GPS.

my only concern is that if your tachometer is reading low, you may be hurting your motor

Well this could be the case. Like I said it is a new tach but I will take it to be tested. I will tell you one thing, the motor did not sound happy at all when I was running 6600RPM according to that tach.

 

[hwsiii]

Re: 4 Way Aluminium Prop Test

I can tell you, I would feel much more comfortable if you have that tach checked out.



H

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

OK, tach has been verified as nearly dead on by a shop tach. Theirs was digital and read <20rpm differance between mine and theirs at 5000 RPM.

I'm convinced now that my numbers are skewed by the tidal currents and wind effects during my test. Even running with current then against in subsequent tests isn't giving an exact representation of prop slip.

This is a great example of how conditions can affect the operation of your boat. During our test yesterday, slip went from 10% while against the current to -3% with the current.

My advice to those reading this is to take the numbers posted above as approximate and will not represent your experience exactly. Please aim to select the prop or props, that will perform best for you under the varied conditions that you will use the boat.

Cheers and thanks for reading!

 

[hwsiii]

Re: 4 Way Aluminium Prop Test

Trend, I do not know where you live in Canada, but if it is anywhere close to the Bay of Fundy or Ungava Bay I definitely understand the Tidal influences you are talking about. The only way to get good/better numbers there is to run cross current, and/or use a boat speedometer instead of a GPS, that way it senses WATER speed and NOT ground speed.



H

 

[trendsetter240]

Re: 4 Way Aluminium Prop Test

H, I am on the west coast of canada in vancouver bc. The tests were performed about 2 miles off shore from the mouth of the fraser river. There are fairly strong tidal, river and wind currents present.

I will test again when I get the chance to run in calm waters. Then again, not everyone will be in calm waters when operating so the test results I have posted should still have some merit.

 

[hwsiii]

Re: 4 Way Aluminium Prop Test

Trend, they definitely have merit, as those are real world conditions you were running in.



H