Testing new prop, Puzzling results, Need advice.

pagick · 17 May 2019, 17:22

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.

pagick · 17 May 2019, 17:47

Here are the two props

jeffstevens763@g · 17 May 2019, 18:48

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

jonp · 17 May 2019, 22:46

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.

pagick · 17 May 2019, 23:13

I bought it used so flipping it isn’t as bad. But what to try next?

jonp · 18 May 2019, 05:56

Quote:

Originally Posted by pagick

I bought it used so flipping it isn’t as bad. But what to try next?

I would speak with solas direct, explaining what you are hoping that gain.

spartacus · 18 May 2019, 06:43

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

The Black Pig · 18 May 2019, 07:25

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

jeffstevens763@g · 18 May 2019, 11:34

https://www.propeller-shop.com/product/3-blade-j70/

worth having a look on here for your engine and prop choice in ss & ali

jwalker · 18 May 2019, 12:36

Quote:

Originally Posted by pagick

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?

jeffstevens763@g · 18 May 2019, 18:28

Quote:

Originally Posted by pagick

Here are the two props

Not sure if it's the photo angle but the ss prop blades look totally different in shape and surface area

Orwell boy · 18 May 2019, 20:16

[QUOTE= a little coincidental - you're not bumping into the rev limiter are you?[/QUOTE]

i reckon both props don,t have enough pitch and are hitting the rev limiter
you need to increase pitch or dia to get the revs down ,just to get a starting point !!, just my opinion !

pagick · 18 May 2019, 22:49

Here are replies to questions posted.

Quote:

Originally Posted by The Black Pig

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

Conditions were windy but I did test in cove with smooth water. Wind to my shoulder. One run north one south then average the two.
I'm in a sib so waxing/polishing isn't an option..or is it?

Quote:

Originally Posted by jeffstevens763@g

Not sure if it's the photo angle but the ss prop blades look totally different in shape and surface area

That adds to the puzzle. Its a semi clever, the aluminum prop is a chopper.
the semi clever feels better once the bow drops. it sinks you in the seat just a touch more but doesn't deliver the top speed.

[QUOTE= a little coincidental - you're not bumping into the rev limiter are you?[/QUOTE]
Im told rev limiter is 6400. I was also told you can feel the limiter. I don't feel anything. I wondered if the tech who did the startup on the new motor changed the factory rev limiter to 6100 but he said he didn't when I called. But did he just forget?

I hate to just shoot in the dark and buy a 21P unless I find a used one or really get confident advice.
I'll call Solas monday and talk to them. But I think the lack of a hard bottom is screwing with what results can be expected. And throws off the advice from prop shops.
Thanks for any further advice posted.

pagick · 18 May 2019, 23:55

Just for fun here is a video I did just after the prop test. I was racing back before the storm hit. Once I got to the lake it was 5mph max for almost an hour. At least the water and all the spray was still 78 deg-f and air 85. I don't know how the boat I passed could go thru the swells in the lake?
https://youtu.be/DVyGSzEivRg

jonp · 19 May 2019, 01:31

A boat I owned two years ago had a two year old Suzuki 90 with a stainless 17 and 17 Ali pitch prop which neither allowed the engine to reach max rpm. After a phone conversation with solas they convinced me to try the same pitch in aluminium but being one of their props which they claimed would be better than the Suzuki props. Once again solas were spot on, not only gaining just over 200rpm but also picking up extra top end speed but most importantly I'd gained 2-3 mph at the engines most economical range of 4500.

The boat I have now was fully setup and tested by the dealer with a 15 pitch prop, which I soon replaced with a solas stainless 13 for once again more top end speed and better cruising at 4500rpm. I'm considering getting an aluminium solas also as they are far kinder on gearboxes than heavy stainles props.

I'm not saying solas are the best props on the plannet ( as I haven't tried lots of makes ) but there advice on getting the right prop for each boat I've owned has been excellent.

By the way your little rib nips along pretty well

pagick · 21 May 2019, 16:06

Well here in US Solas has no phone to call and they are not responding to the inquire form, at least not yet. So I called around and an inflatable dealer said the tach could be off. He sees it every so often a few hundred rpm off. If that's the case I could be bumping into my limiter at 6100. Limiter is 6300-6400.
His wise advice was find your pitch first, then decide if a different prop design is better? With my boat trips space out about every 3 weeks I want to solve this mystery on the next trip.
After finding a online boat suppler that have the best prices on Solas plus a 30% off this weekend I bought two of my original style props. I have a 17P and I ordered a 19P & 21P. The Solas Amita3 cost about $80 each delivered. I can flip them on eBay for close to that if they are unmarked from testing.
I'll follow up with results in a couple weeks.

jeffstevens763@g · 21 May 2019, 19:08

Quote:

Originally Posted by pagick

Just for fun here is a video I did just after the prop test. I was racing back before the storm hit. Once I got to the lake it was 5mph max for almost an hour. At least the water and all the spray was still 78 deg-f and air 85. I don't know how the boat I passed could go thru the swells in the lake?
https://youtu.be/DVyGSzEivRg

Well just watched this looking at your shirt rippling and passing that I think a bass boat as if it was moored up I would be well happy with that performance your boat is rock solid and a nice rig

Roflhat · 23 May 2019, 05:52

If you are getting the same RPM with both but less speed with the higher pitch prop then it is slipping more. You can get some cup added to it which will reduce slip and increase pitch slightly. As a general rule you don't want too much cup on semi cleavers as they are designed to ventilate, but a tiny bit goes a long way and will make a big difference

pagick · 01 June 2019, 00:58

Ok I think I'm in good now with the right pitch. The 19P dropped rpm 200 as expected and also indicated the 6100 (37mph) was probably not the limiter as most of us expected. Or at least that's what I'm going with.
Now the weird result was the 21P I went to right after the 19P and the rpm dropped to 5100 (31mph) thats a big drop. Perhaps the soft hull was just too much drag for a 21P? All tests are averaged from two passes in opposite directions. All props were Solas Amlita3
P.S. the hole shot from original 17P compared to 19P was slightly slower. But the 21P killed the hole shot.

Locozodiac · 01 June 2019, 04:49

Quote:

Originally Posted by pagick

Heres the details-
Zodiac Futura mk2 2013
Evinrude Etec 60hp 2 stroke

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.

Was the sib correctly inflated to factory recommended working pressure, that's with a pressure gauge ? Looking at the posted pic see too much water disorder coming under rear hull, should be flat when riding at speed. Motor seems a bit high seated on transom, ideal would be for water flow to skim right under the upper deflector plate, that's with motor trimmed to 90 deg and deck weight evenly distributed. Check why is the water flow coming in such a disordered manner ?

Happy Boating