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Old 03-11-2019, 08:11 AM   #1
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Default 2000 SR3 Prop spec

Hi all,
I have recently become a Maxum owner and have just joined your site. My name is Andrew, I live in New Zealand near Rotorua.
I have a Prop Question.
Does anybody know what a 2005 Maxum 2000 SR3, 5.0mpi 260hp would have had for an original prop.
The chap I brought it from was running a 14” x 19p Laser2 Prop. Was a dog on hole shot and would rev to 5900rpm.
I have since been working with a prop shop and this weekend tried a 15 x 15p four blade Power Tech Prop. Hole shot was excellent and holding slow speed good but... still reving to 6000rpm. WOT should max at 5000rpm.
Can anyone recall what the OEM prop dimensions were?
Many thanks
Andrew
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Old 03-11-2019, 11:39 AM   #2
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Get a photo tach from an auto store to verify your tachs reading. Not uncommon for these to be off. Try using Quicksilvers prop calculator to see what it recommends.
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Old 03-11-2019, 03:39 PM   #3
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Andrew,
There's something odd with the numbers. I suspect your tachometer is reading incorrectly. 5900 RPM with 19 pitch prop would get you about 70 mph. Also, an engine that could turn a 19 pitch prop at 5900 rpm would give you an absolute monster hole shot.
What RPM do you read at idle? Is tach needle solid or does it drift at times?
Take a look at the back of your tach, does it have a dial that can be set to 4, 6, or 8? Yours should be at 8.
There is a harness on the back of you tach, it will just pull off. Pull off the harness and clean all the contacts.
Do you know your outdrive gear ratio? It should be stamped on the outdrive somewhere, often near the vent plug. We need to know the ratio to get the correct prop, and, someone may have switched outdrives to a different ratio than what came from the factory.
For your 15P run, did you stop at 6000 rpm or was that the limit? How high does your RPM gauge read?
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Old 03-11-2019, 04:03 PM   #4
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The height of the anti-ventilation plate is going to limit how large a wheel you can swing below it. If there was a stock 14" prop and you've gone to a 15", I doubt you're going to be able to get a 16" in there.

The prop change you made doesn't even make a lot of sense to me. If you were 1k rpm's high, you went up 1" in diameter, but down 4" in pitch. It's no wonder you ended up with the same result.

(1" = 200 rpm) 4" reduction in pitch would increase the max rpm another 800 revolutions. The 1" increase in diameter would have decreased max rpm, then the decrease in pitch added another 800 back again.

I would certainly verify the tack is accurate. I would then consider either increasing blades and/or increasing pitch. You might need to do both.
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Old 03-12-2019, 09:49 AM   #5
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Quote:
Originally Posted by jrsick View Post
Andrew,
There's something odd with the numbers. I suspect your tachometer is reading incorrectly. 5900 RPM with 19 pitch prop would get you about 70 mph. Also, an engine that could turn a 19 pitch prop at 5900 rpm would give you an absolute monster hole shot.
What RPM do you read at idle? Is tach needle solid or does it drift at times?
Take a look at the back of your tach, does it have a dial that can be set to 4, 6, or 8? Yours should be at 8.
There is a harness on the back of you tach, it will just pull off. Pull off the harness and clean all the contacts.
Do you know your outdrive gear ratio? It should be stamped on the outdrive somewhere, often near the vent plug. We need to know the ratio to get the correct prop, and, someone may have switched outdrives to a different ratio than what came from the factory.
For your 15P run, did you stop at 6000 rpm or was that the limit? How high does your RPM gauge read?
Thanks for the prompt response.
I am working through all of this.
Ratio of drive is 1.47-1.
It is the original leg from new, I have the documentation from new to confirm.
Idle RPM is 800, a little high... but I do need to change the IDle control valve.

The intent of my post was to find if someone out there has a 2000 SR3 and if they had knowledge of the OEM prop spec.
Andrew
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Old 03-17-2019, 08:17 AM   #6
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Quote:
Originally Posted by shrew View Post
The height of the anti-ventilation plate is going to limit how large a wheel you can swing below it. If there was a stock 14" prop and you've gone to a 15", I doubt you're going to be able to get a 16" in there.

The prop change you made doesn't even make a lot of sense to me. If you were 1k rpm's high, you went up 1" in diameter, but down 4" in pitch. It's no wonder you ended up with the same result.

(1" = 200 rpm) 4" reduction in pitch would increase the max rpm another 800 revolutions. The 1" increase in diameter would have decreased max rpm, then the decrease in pitch added another 800 back again.

I would certainly verify the tack is accurate. I would then consider either increasing blades and/or increasing pitch. You might need to do both.
Hi, I agree... but was trusting the prop shop. At least there was improvement in some areas and it provided starting point data to work from.
Today I picked up another prop to test and gather another set of data.
The change this time is up to 16” diameter and 18” pitch in Four blade SS. Another Power Tech Prop.
I expect to see considerable performance changes.
So... the prop blades are bigger by 1”, should drop RPM. The pitch is greater by 3”, should drop RPM. If each inch of pitch drops RPM by 200, this would make it 5400.
Combined with the larger diameter should bring things pretty much into line. And yes, the 16” fits under the cavitation plate.
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Old 03-17-2019, 11:34 AM   #7
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I still think you need to verify your tach is working properly.
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Old 03-19-2019, 07:08 AM   #8
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Thanks Mmwjr,
I managed to borrow a clip on tach and did indeed find that the tach was incorrect.
There was a small switch on the back that I needed to adjust 2 positions to calibrate to the clip on.
Did a lake test with the clip on still in action and confirmed all is now correct.
So... we now have correct data from the bigger prop. 16” diameter x 18” pitch four blade returned a WOT of 3800-4000rpm depending on trim.
Next to try is a 16” x 16”p 3 blade.

Thanks for the heads up on the tacho issue.
Andrew.
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Old 03-19-2019, 11:26 AM   #9
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Quote:
Originally Posted by Kiwi SR3 View Post
Thanks Mmwjr,
I managed to borrow a clip on tach and did indeed find that the tach was incorrect.
There was a small switch on the back that I needed to adjust 2 positions to calibrate to the clip on.
Did a lake test with the clip on still in action and confirmed all is now correct.
So... we now have correct data from the bigger prop. 16” diameter x 18” pitch four blade returned a WOT of 3800-4000rpm depending on trim.
Next to try is a 16” x 16”p 3 blade.

Thanks for the heads up on the tacho issue.
Andrew.
That selector switch is to set the tach for 4, 6, and 8 cylinder engines. Thought yours was set wrong. I would think a 3 blade 15 1/2 x 17 or 19 would be a better choice for all around performance. Less blade area than a 16" allows for more pitch. Pitch is the distance the prop will more forward for one revolution with no slip. i.e. in a perfect medium.
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Old 03-20-2019, 04:11 PM   #10
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It's typically recommended to have between 15-20% of the propellor diameter for clearance between the blade tips and the hull, strut, anti-ventilation plate.

A 16" prop would need 2.4 -3.2 inches (ideally 20%, so 3.2 inches).
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