www.iFourWinns.com

What props are you running on your 261's.
Mine is twin 460's King Cobra's , props are 14 1/4 19
66mph gps to date.

Greg,

I had a 19p (cupped to 20) stainless on my 211 when I had the 460 KC installed.

You can easily "ballpark" your props by using the following prop-slip calculator.

http://www.go-fast.com/Prop_Slip_Calculator.htm

A single prop (drive) boat would exhibit about 12-15% slip as a rule of thumb (when planing at medium to high speed) for calculations but if you have verified your tachs and are using GPS you can calculate your slip (which should be less since you have 2 drives)

If I remember correctly ALL the drives behind the 460's are 1.41:1 ratio.

I used to get about 60mph at 5000 RPM using a 20P (19 cupped) prop.

With the 454/Bravo III I now get 57mph at 4600, 1.81:1 drive and 26p props (8% slip)

I think with twin drives you might be in the 10-12% (or even lower) slip area but you'd have to measure your speed and RPM accurately to know for sure. (twin counter-rotating props might even be about the same slip as with twin drives.)


Enter the prop-slip calculator with your gear-ratio, pitch and RPM. click CALCULATE under "Theoretical Speed". That will give you the speed you would get if there was NO slip (which is impossible )

Then if you know your actual speed (using GPS or other accurate method like RADAR etc) you can put it in the "ACTUAL SPEED" field and press CALCULATE under the "SLIP" field and it will give you your slip.

Regards,



Rick

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1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

Good site Rick my only problem is I don't have the tachs working yet, hopefully by my next outing.
Gregg

Yeah, until you know what RPM you're turning, you're "shooting in the dark"


The good thing is that if both of your engines are running good and you can sync them (by ear) it's a good bet that if both tachs read the same, they're probably accurate. I would probably still get a known tach and verify them before changing props. Upper max (stock) RPM for your engines is 4800. a tach that's 200 RPM off can throw all the calcs off.....

I have 2 SS props by the way. a 17p SS and the 20p SS.

If anyone wants them, let me know. I'm going to put them on ebay in the next week or so..... along with the rebuilt 650 CFM Holley that was on my 460.



I was going to use the Holley on my 1955 Ford truck 292 Y-Block but it's just too big!

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1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

Hi Rick can you check the part numbers of your carb it should be a 750 for the 460 ? I can help identify.
Gregg

I know it's the original OE carb for my 460 KC because my brother bought the boat new and I was the first one to "touch" it!

According to Holleys "LIST" number, 50399, it's a 650. http://www.holley.com/data/TechService/ ... isting.pdf (see pg 13)

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1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

Rick I just checked those part numbers in my OMC service manual and it comes up 750 cfm I will try and do some more research I have all the holley books.
Gregg

Rick I just googled National Carburetor 9015 , 750cfm ford .
Gregg

Gregg,

THANKS! That's good to know. That carb is just TOO BIG for my little 292 Y-Block. It's a shame too since I spent all that money re-building it!

It's got the OEM OMC Flame arrester. I guess I'll put them both on ebay or something!

I also have a power steering actuator, pump, hoses, and cooler for a 460. I'll throw that stuff on there too.



Wish me luck!


R

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1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

Hey Rick,
I will have to look this weekend, but I think my 460's have 650's on them. They are marine as well.
If that is so, maybe we can work out a swap or something.......................

I am sure that if I have 650's, it will not be enough for the 472's at over 10 to 1 compression they have.
I don't like to choke engines on air flow if I don't have to, I would rather jet them down some if they are
real hogs....

If I don't like how these Holly's run, I will be putting on Edlebrocks in a hearbeat.

JV

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1992 Baja 38 Special Twin 502 Mags

03 Stingray 3.0
88 261 Liberator 460 King Cobras
95 Bayliner 1850 3.0
77 Fiber Form 20ft 350/385hp
70 Wescraft 1800 SS 455 Jet

Lead, Follow, or get the Hell out of the Way!

Hey thanks.

I sort of figured that I'd need to use a smaller carb for the truck. Even 600 cfm is a bit much for my lil 292!

It's all rebuilt and is balanced. It's also got a little higher compression than a stock one.
It's going in front of an recently rebuilt E4OD automatic.

YES I have pictures of it as well!!


.....


Ok....you probably want to see the truck too?

I plan to tow the Liberator with it!!

Um.....it's the green one on the right!!

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1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

Rick that truck and engine is way cool, its crying tri power
Gregg

Yeah, I looked for a tri-power manifold for a while.....They want a fortune for them.

I friend of mine who is a flat-head rebuilder told me if it was for a street car it would work fine. He said for a truck I should just get a good 4 bbl.


I also have a 2 speed electric rear axle for it too! The trans has a lock-up TC and 0.71 OD!

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1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

I have 4 blade 22P Bravo I on both of mine.
I don't like the thought of how much more power that gets robbed with the 4 vs the 3 blade, but I'll know as soon as I get them going in a couple of weeks.

_________________
1992 Baja 38 Special Twin 502 Mags

03 Stingray 3.0
88 261 Liberator 460 King Cobras
95 Bayliner 1850 3.0
77 Fiber Form 20ft 350/385hp
70 Wescraft 1800 SS 455 Jet

Lead, Follow, or get the Hell out of the Way!

Don't just about ALL of the "Go-fast" boats have 3 blade props instead of 4 blade?

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1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III