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Old 17 May 2019, 12:22   #1
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Testing new prop, Puzzling results, Need advice.

I went out test my new "used" prop that was suggested would get me 4-5 mph more by two different dealers. But it tests out to be 1 mph lower?
Heres the details-
Zodiac Futura mk2 2013
Evenrude Etec 60hp 2 stroke
Original prop- Solas Amita 3 aluminum 13.25 X 17P top speed 35mph 6100rpm
new prop Evenrude Viper Stainless 13 7/8 X 19P. top speed 34mph 6100 rpm
The new prop did seem to have a touch more punch once the bow drops but only noticeable when swapping back and forth.
Last season the original Solas is delivering 2 mph more but the water was a slight bit rougher on the test day.
Question 1 How could the results be so similar with such a pitch/material difference?
I was exception tho have my rpm drop about 300-400 as well as gain a few mph with the new prop.
Question 2 Looking at the picture should I raise the motor? I did have it up one hole at first but it would ventilate when you trimmed up any. Now that I have some good video it looks low. Also this screen capture was after trimming just below where you hear ventilation.
Thanks for any advice.
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Old 17 May 2019, 12:47   #2
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additional pics

Here are the two props
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Old 17 May 2019, 13:48   #3
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You will get 5% more out of the stainless prop in terms of performance your increase in dia and pitch add together if both were aluminium you would have seen more of a drop in speed IMO
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Old 17 May 2019, 17:46   #4
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I find the fact your max rpm is the same quite odd, normally a stainless of the same pitch and diameter will reduce rpm. It was once a fact that stainless props performed slightly better than aluminium due to thinner diameter blades and better shaping of the blades, these days this isn't true so much. Solas aluminium props perform very well, I've chosen them over certain stainless props on several boats ( my last three ) . However I currently have a solas Saturn stainless which performs very well. With my current stainless I dropped from a Yamaha 15 pitch aluminium to the solas 13 stainless to gain to 200 rpm and 2mph ( 5700rpm -5900rpm ) .

There are some makes of stainless that are poor in design and performance, just because they are stainless doesn't mean they will perform better than a well designed aluminium prop. Are you able to return the stainless and try any others ( this is something solas allows ). Solas will normally send you the correct prop from the details you provide them on your currant prop, rpm and intended use.
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Old 17 May 2019, 18:13   #5
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I bought it used so flipping it isnít as bad. But what to try next?
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Old 18 May 2019, 00:56   #6
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Originally Posted by pagick View Post
I bought it used so flipping it isnít as bad. But what to try next?
I would speak with solas direct, explaining what you are hoping that gain.
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Old 18 May 2019, 01:43   #7
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That is surprising. You'd expect the 19 pitch to give you better top speed.

Looking at Solas propellers, they do stainless steel 21" Saturn, part number 2431-130-21. That said, you might be better sticking with aluminium given costs involved. They do Amrita 3 at 13.0 x 21 pitch, part number 2411-130-19 and larger blade 13.2 x 21 pitch, part number 2411-132-21. There's always a compromise in achieving top speed, as the lower pitch propellers give you a better hole shot from standing start.

I know the Tohatsu guys rave about Michigan Ballistic propellers.
https://www.deepblueyachtsupply.com/...t/90?fltr=7|21
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Old 18 May 2019, 02:25   #8
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Were the conditions exactly the same friction plays a huge part
Wind and waves even the condition of your hull ( polished hulls increase speed )will all affect speed
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Old 18 May 2019, 06:34   #9
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https://www.propeller-shop.com/product/3-blade-j70/

worth having a look on here for your engine and prop choice in ss & ali
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Old 18 May 2019, 07:36   #10
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Quote:
Originally Posted by pagick View Post
I went out test my new "used" prop that was suggested would get me 4-5 mph more by two different dealers. But it tests out to be 1 mph lower?
Well there's lesson number 1....

Quote:
Question 1 How could the results be so similar with such a pitch/material difference?
Plainly they both load the motor similarly but the aluminium prop is more efficient.

You're comparing two completely different propellers, about the only thing they have in common is they are both propellers and they both have three blades. Both revving to 6100 does seem a little coincidental - you're not bumping into the rev limiter are you?
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