Forums
NautiqueParts.comNautiqueSkins.com - Correct Craft Upholstery and Part
  New Posts New Posts RSS Feed - Prop help for my Southwind on steroids
  FAQ FAQ  Forum Search   Register Register  Login Login

Prop help for my Southwind on steroids

 Post Reply Post Reply Page    <12
Author
MrMcD View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: January-28-2014
Location: Folsom, CA
Status: Offline
Points: 3687
Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: May-17-2024 at 1:35pm
No problems with the prop logic, I struggle with the 1/4" clearance between the prop and hull, that just seems like a problem in the making?   I would feel better if it was at least 1/2" clearance but I am no prop expert.
Back to Top
DenDen View Drop Down
Senior Member
Senior Member
Avatar

Joined: July-20-2023
Location: USA
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote DenDen Quote  Post ReplyReply Direct Link To This Post Posted: May-21-2024 at 11:29pm
It seems that I either need a 430 13 x 13 or a 474 13 x 12 5/8.
Both at .080 cup.
What is the expected RPM difference between a 1 inch change in pitch?
If it is as low as 200 RPMs, then these two props are basically the same. If it’s as high as 1000 RPMs, then the difference between these two props is 300 RPMs.
My understanding is by changing the cup. You could turn either one of these props into the other.
So my big question is why do they make so many props so close together?
I am still confused, but getting close.
Is it better to start with a big prop and trim it down or start with a little prop and build it up?

Back to Top
JoeinNY View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: October-19-2005
Location: United States
Status: Offline
Points: 5698
Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: May-22-2024 at 5:26pm
Originally posted by DenDen DenDen wrote:

It seems that I either need a 430 13 x 13 or a 474 13 x 12 5/8.
Both at .080 cup.
What is the expected RPM difference between a 1 inch change in pitch?
If it is as low as 200 RPMs, then these two props are basically the same. If it’s as high as 1000 RPMs, then the difference between these two props is 300 RPMs.
My understanding is by changing the cup. You could turn either one of these props into the other.
So my big question is why do they make so many props so close together?
I am still confused, but getting close.
Is it better to start with a big prop and trim it down or start with a little prop and build it up?



You would need to know your torque curve and where your current prop fell rpm wise to even make a guess at rpm’s per inch of pitch. Your understanding of cup is flawed at best and while it is possible to change cup or trim down the diameter of a cnc propeller it is not free and is now way to live.   You want the fresh cnc goodness’s.   I’ve got a boat that runs 5000 with a borrowed 431 and I bought it a fresh 475 hoping to get a few more rpm out of it - it’s 61 years old so I am hoping to give it a little easier time.
- you’ve been given the best advice you are going to get knowing what you know, but a prop and go boating
- or wait a few weeks and I’ll tell you the difference between the two props on a completely different boat with a completely different engine
1983 Ski Nautique 2001
1967 Mustang 302 "Decoy"
Holeshot Video
Back to Top
DenDen View Drop Down
Senior Member
Senior Member
Avatar

Joined: July-20-2023
Location: USA
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote DenDen Quote  Post ReplyReply Direct Link To This Post Posted: May-22-2024 at 6:08pm
Thanks for everyone’s help and advise it is much appreciated as usual.
I will post my findings and what Prop I decided to go with. Delta Prop is like half an hour away from me in Cleveland and will give me at least one free adjustment for what that’s worth.
Back to Top
63 Skier View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: October-06-2006
Location: Concord, NH
Status: Offline
Points: 4266
Post Options Post Options   Thanks (0) Thanks(0)   Quote 63 Skier Quote  Post ReplyReply Direct Link To This Post Posted: May-22-2024 at 9:48pm
What Joe was trying to say was, don't plan on any adjustments to the prop.  Buy a CNC per the advice above and run it.  By running it and then "adjusting" you'll end up with worse performance than by simply running a correctly sized prop.

I found when I was first reading about modern props that the couple of rules I thought I knew about props were out the window.  I think in the past people would do a bunch of trial and error, bring their prop in for more cup or to cut down the diameter as you are talking about, but they were adjusting a prop that was perhaps adequately designed but not precise, so maybe the adjustments would help performance because the base product wasn't all that great to start with.
'63 American Skier - '98 Sport Nautique
Back to Top
KENO View Drop Down
Grand Poobah
Grand Poobah


Joined: June-06-2004
Location: United States
Status: Offline
Points: 10915
Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2024 at 8:33am
I guess it's time for a little update on Den's prop story.

He wanted to drop his full throttle rpms down to around 4500, so after getting some input here and from various other places he got a new Acme 13x14 from Delta propeller on their recommendation (with one free rework if needed) and got some new baseline numbers you could say.

Same tach and GPS as before, he had some new numbers 35 mph at 3000 rpm, 45 mph at 4000 rpm and 49 mph at 42 to 4300 rpm and plenty of acceleration

He's sorta happy but he'd be happier at 4500 or maybe a little higher rpm.

I "gently" reminded him that nobody here had recommended that prop saying it was too much prop and would do just what it did.

I'm sure he'll update with his next step which will involve talking to Delta about picking up about 3 to 500 rpm. whether it's with a prop swap or a rework of what he has now

Just to repeat it again, he wants to stay at or a little above 4500 rpm at full throttle.

Myself, I think the answer was in the thread, but that's how you learn, get a bunch of input then take your best shot and go from there  Wink

In the meantime, I think he may be on vacation enjoying some cruisin' in his boat (or will be soon)
Back to Top
fanofccfan View Drop Down
Platinum Member
Platinum Member
Avatar

Joined: December-13-2009
Location: North Bend NE
Status: Offline
Points: 1762
Post Options Post Options   Thanks (0) Thanks(0)   Quote fanofccfan Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2024 at 8:46am
Thanks for the update Ken!  Seems like a speedy boat 
2004 196 LE Ski 1969 Marauder 19 1978 Ski
Back to Top
KENO View Drop Down
Grand Poobah
Grand Poobah


Joined: June-06-2004
Location: United States
Status: Offline
Points: 10915
Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2024 at 8:51am
Seems it, I can't decide if it's the little brother of the BFN or the mother of the BFN.

I think it was the mother as the story goes. Wink
Back to Top
JoeinNY View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: October-19-2005
Location: United States
Status: Offline
Points: 5698
Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2024 at 10:39am
That all sounds about right - if for some reason I was dead set on overloading an engine with too much prop, or just in a position where it was the only prop I had to run and needed to get some recreation in, then I would make some adjustments to prevent knocking/destructifyering.   Specifically consider dialing back a couple/few degrees of timing. Could also give it a bit more fuel jetting and or higher octane gas - particularly if you are going to pull watersports.   450 dollar experiments need not become 4500 dollar season enders.
1983 Ski Nautique 2001
1967 Mustang 302 "Decoy"
Holeshot Video
Back to Top
DenDen View Drop Down
Senior Member
Senior Member
Avatar

Joined: July-20-2023
Location: USA
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote DenDen Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2024 at 11:21am
Thanks for all the kind input.
We are currently trying to make sure our engine is outputting as much horsepower as possible. We have no signs of detonation and yesterday we fattened it up with some carburetor jetting and ran it again. The result was 4300 RPMs and 51 mph.
I will be going to a big lake at the end of the week for a while and will experiment with the jetting some more.
This is a cruising vacation with no skiers or tubers. So what I have will work just fine for now thanks again for all your help.
Back to Top
63 Skier View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: October-06-2006
Location: Concord, NH
Status: Offline
Points: 4266
Post Options Post Options   Thanks (0) Thanks(0)   Quote 63 Skier Quote  Post ReplyReply Direct Link To This Post Posted: June-04-2024 at 8:34pm
The 51 mph at 4300 surprises me.  You upgraded power to a bit over 300 hp so that I guess explains it.
'63 American Skier - '98 Sport Nautique
Back to Top
DenDen View Drop Down
Senior Member
Senior Member
Avatar

Joined: July-20-2023
Location: USA
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote DenDen Quote  Post ReplyReply Direct Link To This Post Posted: June-15-2024 at 8:08am
Update
After vacation still same 4300 RPMs and 51 mph. Perform really nice I guess due to my nature I’m going to go against the advice of knowledgeable people and send it back to Delta to have them add six or 700 RPMs.
Will advise hopefully soon the results.
Back to Top
KENO View Drop Down
Grand Poobah
Grand Poobah


Joined: June-06-2004
Location: United States
Status: Offline
Points: 10915
Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-15-2024 at 8:43am
Looks like you're trying for 5000 ish  now like was mentioned plenty in this thread instead of 4500 ..........sounds like a good plan to me anyways Wink
Back to Top
GottaSki View Drop Down
Grand Poobah
Grand Poobah


Joined: April-21-2005
Location: NE CT
Status: Offline
Points: 3345
Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: June-17-2024 at 8:48am
"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."

River Rat to Mole
Back to Top
DenDen View Drop Down
Senior Member
Senior Member
Avatar

Joined: July-20-2023
Location: USA
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote DenDen Quote  Post ReplyReply Direct Link To This Post Posted: July-09-2024 at 8:11pm
I bet some of you were wondering what happened to Den Den.
Since I went to Lake Norman came home sent my prop out and had it decupped, I have not had the boat in the water. It may be a couple of weeks before the final test.
But I have been thinking about purchasing a prop and the procedure to go through.
It all seems to be a guessing game of sorts at the expensive the guy buying the Prop
I say that because the only thing a person can do is look for recommendations from people who are supposed to know what prop you need.
In my case, I was recommended at one time a 13 x 11 , a 12,5 x 11.5, a
13 x 12.625, a 13 x 13, and a 13 x 14.
All I had to do was make the choice and see what worked.
Kind of a guessing game? especially since the boat was a south wind 18 which there are very few of.
I’m pretty confident I’m going to be close to what I wanted going the route I chose. I also know I could’ve probably taken another route and ended up maybe the same place.
It seems to me there should be a better way to sell propellers, but I do understand the difficulty in returning props that are wrong or perform poorly.
That’s all I have right now. I will post my findings when I get the boat in water again.
I hope everyone is having a great summer.
Back to Top
JoeinNY View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: October-19-2005
Location: United States
Status: Offline
Points: 5698
Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: July-09-2024 at 9:47pm
Unfortunately propeller shops or manufacturers can’t afford to buy a bunch of boats and engines. Boat manufacturers can’t try new props on old boats to keep up on what might run right, and when you put an engine in a boat that’s never been there then all bets are off. A few people have spent way too much time
and money buying multiple boats, conducting multiple engine upgrades, and buying many props per boat/engine- blowing some up - skiing for years successfully behind others - and they get persnickety when that advice not accepted as gospel immediately. If you only bought one incorrect prop and learned who to trust on the next one then you did pretty well.
1983 Ski Nautique 2001
1967 Mustang 302 "Decoy"
Holeshot Video
Back to Top
DenDen View Drop Down
Senior Member
Senior Member
Avatar

Joined: July-20-2023
Location: USA
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote DenDen Quote  Post ReplyReply Direct Link To This Post Posted: July-09-2024 at 11:57pm
Well said!!!!
I couldn’t agree with you more.
Back to Top
63 Skier View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: October-06-2006
Location: Concord, NH
Status: Offline
Points: 4266
Post Options Post Options   Thanks (0) Thanks(0)   Quote 63 Skier Quote  Post ReplyReply Direct Link To This Post Posted: July-10-2024 at 12:36am
I agree well said Joe.  One other thing I'd add ... we all want the best prop for our boats, but honestly perfection isn't necessary.  So it spins a few hundred rpm too low or too high, WOT is a few mph lower than expected, whatever (not meaning your boat DenDen, just saying for any of us).  I have 2 props for my Sport, decided which I preferred but a few people I ski with might prefer the other one.  Neither is perfect, each has it's benefits and drawbacks.  At some point we just want to launch and spin the hour meter and enjoy the boat.
'63 American Skier - '98 Sport Nautique
Back to Top
KENO View Drop Down
Grand Poobah
Grand Poobah


Joined: June-06-2004
Location: United States
Status: Offline
Points: 10915
Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-10-2024 at 7:43am
Originally posted by DenDen DenDen wrote:


In my case, I was recommended at one time a 13 x 11 , a 12,5 x 11.5, a
13 x 12.625, a 13 x 13, and a 13 x 14.

I think you missed one Den Wink

Get that thing in the water and do some enjoying.

63 Skier said it well
Back to Top
DenDen View Drop Down
Senior Member
Senior Member
Avatar

Joined: July-20-2023
Location: USA
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote DenDen Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2024 at 11:40am
Finally a conclusion.
Took the boat out specifically for high-speed test runs. After five runs from idle to wide-open throttle-top speed.
The result is 4700 RPMs 50 mph. That’s kind of a round average numbers and with two people in the boat,
Both into the wind and with it.
Everything seems to be great!
The thing starts, idles, accelerates, sounds great.
It seems as if it may have just left the Correctcraft factory in 1975 with a little more horsepower than it originally had.
Going to take the great advice above and enjoy it.
That completes everything on this rebuild and I appreciate all the help and time everyone gave me to accomplish this. It is a great boat and gets a lot attention.
Back to Top
KENO View Drop Down
Grand Poobah
Grand Poobah


Joined: June-06-2004
Location: United States
Status: Offline
Points: 10915
Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2024 at 12:01pm
I think I hear ol' blue eyes in the background singing " I did it my way" Wink
Back to Top
63 Skier View Drop Down
Grand Poobah
Grand Poobah
Avatar

Joined: October-06-2006
Location: Concord, NH
Status: Offline
Points: 4266
Post Options Post Options   Thanks (0) Thanks(0)   Quote 63 Skier Quote  Post ReplyReply Direct Link To This Post Posted: July-15-2024 at 4:15pm
Congrats on the boat, a 49 year old Southwind 18 running 50 mph sounds very healthy to me!
'63 American Skier - '98 Sport Nautique
Back to Top
 Post Reply Post Reply Page    <12
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Copyright 2024 | Bagley Productions, LLC