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427 LS pushin a 3 blade s pitch limits

Posted: Mon Nov 30, 2015 1:24 am
by aggiejim
Ive got a heavy 18 foot boat 3'4 deck 3/16 bottom im pushing a 82 inch s blade with a 2.3 century belt drive at what point does to much pitch become counter productive allmost to the 3 point now and can still turn 5500 rpm I know there is a point of deminishing return on pitch yes I can go 4 blade but at what point do i make that call, can use a little input

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Mon Nov 30, 2015 7:22 am
by SWAMPHUNTER45
If you read the Sensenich installation data you will see they actually refer to a pitch setting of "4" so going slightly over the 3 mark is not a point of terminal performance.

When I visited Darrin a few weeks back we spent some time discussing prop settings. It was explained to me to think of a prop blade as a wing. As such, you can continue to add pitch as long as you see a desired effect. Eventually you will hit a point where the blade will stall. At this point you will no longer gain thrust and may see a increase in rpm. Now that is the ultra simple layman's 100 word or less explanation. Before you purchase the 4 blade try pitching to about the 3.25 area, I think your going to see results.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Mon Nov 30, 2015 8:53 am
by Joe
What diameter is your 3 blade? The S blades are so wide that anything over the 3 and your just slapping air rather than moving air. There not like the R or other blades that do well over pitched. There has been alot of discussion about the S blades on here. You could do a search. But be pending on your diameter is now you might benefit more by increasing length. If your under 82 inches your better off going bigger if you can. I run S blades.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Mon Nov 30, 2015 9:40 am
by crowhater
aggiejim wrote:Ive got a heavy 18 foot boat 3'4 deck 3/16 bottom im pushing a 82 inch s blade with a 2.3 century belt drive at what point does to much pitch become counter productive allmost to the 3 point now and can still turn 5500 rpm I know there is a point of deminishing return on pitch yes I can go 4 blade but at what point do i make that call, can use a little input

Agg, I have run the S blade in ( 3B and 4B ) configuration both with a ( 2.3 & 2.6 ) reduction on a 700hp engine with 300shot of nitrous. So I think it is fair to say I have swung the S blades pretty hard over the years. On the same day I tried the 3 blade and the 4blade of the same boat to see if more pitch with less blades did better than more blades with less pitch. ( boat 18x18 Red River, VERY HEAVY BOAT ). I can tell you for a fact that once you go past the #2 pitch mark you are wasting power paddling the air! The 3 blade with a bunch of pitch Sucked compared to the 4 blade pitched at 2. Having those blades pitched like that also make your tow vehicle fuel mileage suck.

Another thing to consider! I was one of the first people to put a 4 blade 82" S on a 2.68 reduction with a 530CI Cadillac. This was a big torque engine and I was spinning the blades like they were toys. No one could believe I was spinning these blades pitched past the 3 mark with ease to 5200rpm. A member asked me about my cage and I told him I had expanded steel on my cage and he explained that was the problem. The expanded steel I purchased was from McNichols steel and suppose to flow air 80%. When I removed the expanded steel and put 4x4 wire on my cage I had to reduce my pitch to #2 because my engine could not turn the prop with any more pitch.

Any time I ran the S blades with more than 2-2.5 pitch I would see diminishing returns and the engine would push more oil mist out of my valve cover breathers.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Mon Nov 30, 2015 12:37 pm
by SWAMPHUNTER45
The aero package on every boat is different so it doesnt cost anything to try a little more pitch. Crow has a lot of "S" blade time so chances are your going to see more gains by spending money but the rule of mods is start with the free kind first.

Let us know your findings

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Mon Nov 30, 2015 1:18 pm
by Waterthunder
If your not at 3rd mark yet and turning 5,500 there is enough pitch left to choke it down. What RPM are you shotting for,,, 5,200 or so. 300RPM's aint far off and your not at the 3rd mark yet I would set it on 3 and see what you turn!!!.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Mon Nov 30, 2015 10:22 pm
by aggiejim
I dont think I can get any less restriction on the blades

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Tue Dec 01, 2015 10:31 am
by Waterthunder
WOW you could change some things and I bet you could only turn that prop around the 2nd mark. There is a ton of things you could do to clean up that rig. Even better you can change somethings and do some testing and find out what helps and what doesnt an it wouldn't cost you a dime.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 11:25 am
by aggiejim
I would shure be interested in hearing more I went to a lot of trouble to clear up air stream

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 1:52 pm
by Tony480
You didn't do a very good job. Lol

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 4:03 pm
by SWAMPHUNTER45
One thing I would consider changing is your solid "foot locker" style seat base.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 4:54 pm
by ranger1424
Hey Jim saw your boat when we run together up on the red, what these guys are trying to tell you is you are starving your prop, reason you can turn it up is not too much horsepower rather air starvation, simple way to learn this is take a box fan cut two pieces cardboard, one same size as box other half size of box, turn fan on high, put half sheet cardboard on back[suction] side of fan, take it off and put full sheet on suction side, blades will 'speed up' more you starve them ,you did not change horsepower, you unloaded the blades. Reason you can spin those blades is you are starving them, unloading them, you will be AMAZED if you clean up in front of the cage, will have to lose some pitch to turn them. Later my friend see you on the river, nice boat, know your enjoying it. Later

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 5:15 pm
by akblackdawg
if he is starving his with that little box, mine is really gasping for more air. Bud

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 5:26 pm
by ranger1424
EXACTLY why your able to turn the wide blades, no air to LOAD prop.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 5:37 pm
by Tony480
Yep...and why those boat's will never run like they should

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Thu Dec 03, 2015 6:50 pm
by Rich Andrews
best post in a while... even w Tony's input:)

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Fri Dec 04, 2015 1:22 am
by aggiejim
I will build a mesh wire seat stand damm there is a lot of electronics in that box breakers fuses disconnects charging station for headsets radio, amp speakers and true dry storage that will be missed damm the good ideas.

Thanks for the insight Jim

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Fri Dec 04, 2015 7:10 am
by SWAMPHUNTER45
Would it be possible for you to do a little testing before running out and fabricating?

1) I would suggest if not to complicated, warming up the engine and doing a full power run up on video capturing your boats current gauge data. You will then have the ability to watch the runs over again and really focus on the data in comfort.

2) Remove the seats and the foot locker and repeat the full power run up on video and compare your data.

3) Study any other potential aero obstructions and search for what may be able to enhance air flow.
1) fuel cell location and shape
2) coolers or obstructions in air stream
3) seat height
4) consoles
5) mesh size

Personally I find my rod boxes or a partial deck over design to hinder air flow but I have so scientific data.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Fri Dec 04, 2015 8:19 am
by flying fish
Jim
No need to change your seat stand(foot locker) she aint a race boat, and I have seen her in action. Dang nice family ride.

I would think just adding a small amount of pitch 1/2 pitch mark or less would choke her down to where you want. If she is slapping air, you will know real quick.

IMO- add length if you have to make a change. Sure appears you could add 2" prop length and be able to back off on pitch staying with a 3 blade.

Your top seat stand is a fine looking addition to your ride.
Family ride boat. -Performance don't equal how fast you get from point A to B, but how comfortably you get there and absolutely how good your ride looks when you arrive. :)

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Fri Dec 04, 2015 8:42 am
by glades cat
From the pics, it looks like your radiator is mounted vertically. I've seen where the radiator is mounted angled forward and it has restored the airstream to the bottom blades and not affected engine cooling.

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Fri Dec 04, 2015 1:14 pm
by SWAMPHUNTER45
Great info Glades I may try that myself on my repower

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Wed Dec 09, 2015 12:20 am
by aggiejim
re pitched the props to just past 3 5200 rpm 3000 cruse and that heavy ass boat ran dry texas sand that is more than ever expected thanks guys leaving the boat the way it is I really like the configuration great ride and fishing boat

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Wed Dec 09, 2015 5:27 am
by jimbo_jwc
ranger1424 wrote:Hey Jim saw your boat when we run together up on the red, what these guys are trying to tell you is you are starving your prop, reason you can turn it up is not too much horsepower rather air starvation, simple way to learn this is take a box fan cut two pieces cardboard, one same size as box other half size of box, turn fan on high, put half sheet cardboard on back[suction] side of fan, take it off and put full sheet on suction side, blades will 'speed up' more you starve them ,you did not change horsepower, you unloaded the blades. Reason you can spin those blades is you are starving them, unloading them, you will be AMAZED if you clean up in front of the cage, will have to lose some pitch to turn them. Later my friend see you on the river, nice boat, know your enjoying it. Later
Best way to understand is playing with box fan to understand flow and load . I had noticeable performance improvement when changing fuel tank and moving my radiator up to the front of the engine , plus less junk strikes on blade and radiator .

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Wed Dec 09, 2015 6:20 am
by SWAMPHUNTER45
That's awesome!

Glad it worked for you :cheers:

Re: 427 LS pushin a 3 blade s pitch limits

Posted: Wed Dec 09, 2015 8:30 am
by Deano
Very Cool, Indeed. :headbang:
It's always refreshing to hear that the easiest, most cost effective fix was the correct one. 8)

That seems to happen somewhat infrequently.