Tahoe 23 prop size?

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Brad Tucker
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Tahoe 23 prop size?

Postby Brad Tucker » Mon Jul 10, 2017 7:49 am

I am trying to figure out which prop size I need for my Tahoe23. I would love to have at least a good starting point, then fine tune from there If needed. The current information I know is this:
Set up for 13" prop
351V8 rated at 240 hp
WOT RPM 4400
cruise RPM 3600
Weight 3500 lbs (educated guess, AKA SWAG)

Weight is a guess, based on Butch's Tahoe. I subtracted from his weight the difference between BBChevy and SB Ford, approximate weight of the stretch, and approximate weight of an extra ply layer.

I don't expect to be pulling skiers anytime soon. I appreciate any information anyone with the knowledge could provide. It would at least get me in the ballpark. My best current plan is to start with a 13x13 and go from there.

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Bill Edmundson
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Re: Tahoe 23 prop size?

Postby Bill Edmundson » Mon Jul 10, 2017 12:36 pm

Brad

What is you gear ratio? Then I'll take a stab at it.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

Brad Tucker
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Location: Washington, GA

Re: Tahoe 23 prop size?

Postby Brad Tucker » Mon Jul 10, 2017 12:48 pm

1:1. Sorry, I meant to mention that.

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Mr Hot Rod
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Re: Tahoe 23 prop size?

Postby Mr Hot Rod » Mon Jul 10, 2017 2:00 pm

Brad,

Here's an Excel spreadsheet which might be useful. It will provide you with SHP required to maintain a given speed :

Input Specs :

    • 351V8
    • 240 hp
    • WOT RPM 4400
    • Cruise RPM 3600
    • Gear Ratio : 1:1
    • Weight 3500 lbs (educated guess)
What's missing is desired maximum speed (MPH).

We've specified the following parameters : MPH = 50 MPH, Displacement of 3200 lbs. and 3500 lbs.

Analysis :

    • The spreadsheet calculates two different engines with four gear ratios :
    12% overdrive, 1:1 direct drive, 1.25:1 and 1.50:1 reduction ratios.
    • At the bottom of the spreadsheet, you'll find notes about the Optimum Pitch Formula.
    • Red cells indicate props with ideal PD (Pitch/Diameter) Ratios.

    Image
    Click the image to see the PDF document.

Recommended Ratios and 3 Blade Propellers :

    Required speed 50 MPH, weight 3200 lbs., 240 HP @ 4400 RPM : .88 / 11x15, 1.00 / 12x17
    Required speed 50 MPH, weight 3500 lbs., 240 HP @ 4400 RPM : .88 / 11x15, 1.00 / 12x17

Feel free to download the spreadsheet and modify it to suit your needs :


More info and calculators on our website's Propeller Page.

Hope this helps !
________________________________________
Paul Kane
Kane Custom Boats Ltd.
Chelsea, Quebec

Building the Glen-L Hot Rod : http://www.kanecustomboats.com
Glen-L Hot Rod build thread
Kane Custom Boats YouTube channel
Glen-L Boat Video Directory
Last edited by Mr Hot Rod on Mon Jul 10, 2017 4:37 pm, edited 3 times in total.

Brad Tucker
Posts: 319
Joined: Tue Jun 29, 2010 7:20 am
Location: Washington, GA

Re: Tahoe 23 prop size?

Postby Brad Tucker » Mon Jul 10, 2017 3:09 pm

Thanks Paul! So, according to your work, a 12×17 should push a 3500lb boat 45mph at WOT with 238hp. Am I reading that correctly?

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Mr Hot Rod
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Re: Tahoe 23 prop size?

Postby Mr Hot Rod » Mon Jul 10, 2017 3:39 pm

That's correct. You'd have to add 36 HP to go 50 MPH.

Download the spreadsheet and specify Required maximum speed = 45 MPH.
This is a great tool for determining gearing, SHP and Speed. Of course this would require an engine in top mechanical condition (sufficient HP and Torque) to attain the required speed.

____________________
Paul Kane
Kane Custom Boats Ltd.
Chelsea, Quebec

Building the Glen-L Hot Rod : http://www.kanecustomboats.com
Glen-L Hot Rod build thread
Kane Custom Boats YouTube channel
Glen-L Boat Video Directory
Last edited by Mr Hot Rod on Mon Jul 10, 2017 4:28 pm, edited 1 time in total.

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Bill Edmundson
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Re: Tahoe 23 prop size?

Postby Bill Edmundson » Mon Jul 10, 2017 4:04 pm

Brad

Paul is definitely the man. I think 12x17 is damn close. I don't think at your RPMs you need to go larger than a 12" prop. I run about 115 HP with a 13x16 prop. at 3100 prop RPM at can run 38 Mph.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

Brad Tucker
Posts: 319
Joined: Tue Jun 29, 2010 7:20 am
Location: Washington, GA

Re: Tahoe 23 prop size?

Postby Brad Tucker » Mon Jul 10, 2017 4:11 pm

Bill and Paul, thank you very much for the information. Going about it like a blind hog hunting acorns wasn't going to be fun.

Brad Tucker
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Re: Tahoe 23 prop size?

Postby Brad Tucker » Mon Jul 10, 2017 4:41 pm

And, a 12x17 isn't just a click away on the net. Acme has a 12.25x15.25 in a 1" bore, then they go to 13"s.

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Mr Hot Rod
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Re: Tahoe 23 prop size?

Postby Mr Hot Rod » Mon Jul 10, 2017 5:16 pm

We never said that this process was going to be easy !

OJ Legend 3-blade sizes

    Part Number / Specs :

      1008 / 12X15 LC 1"
      1010 / 12X15 RC 1"
      1012 / 12X16 LC 1"
You can also have a 15 or 16 pitch propeller repitched, or have a larger diameter 17 pitch propeller cut down to 12".

The Glen-L Inboard Hardware Catalog lists a prop that is very close to what you need :
____________________
Paul Kane
Kane Custom Boats Ltd.
Chelsea, Quebec

Building the Glen-L Hot Rod : http://www.kanecustomboats.com
Glen-L Hot Rod build thread
Kane Custom Boats YouTube channel
Glen-L Boat Video Directory

Brad Tucker
Posts: 319
Joined: Tue Jun 29, 2010 7:20 am
Location: Washington, GA

Re: Tahoe 23 prop size?

Postby Brad Tucker » Mon Jul 10, 2017 5:36 pm

You could have warned me! :lol: I knew about the GL one, and it is close. Maybe close enough. There is an inboard specialty close to me who will let you run a prop for 30 days and swap it out for another if not satisfied. If I went up in diameter and down in pitch, is there a such thing an equivalent prop? I can go to 13". Or, from 3 blades to 4? Or both?

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Bill Edmundson
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Re: Tahoe 23 prop size?

Postby Bill Edmundson » Mon Jul 10, 2017 6:25 pm

Brad

I have a 12x17 LH 1" that I can sell you. New bronze. I'm happy with the 13x16 I have. It is down at Gulf Shores.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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Mr Hot Rod
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Re: Tahoe 23 prop size?

Postby Mr Hot Rod » Mon Jul 10, 2017 6:55 pm

Brad,

Download the Diameter-HP-RPM Formula spreadsheet from our website and input your specs :
More light reading from our website :


____________________
Paul Kane
Kane Custom Boats Ltd.
Chelsea, Quebec

Building the Glen-L Hot Rod : http://www.kanecustomboats.com
Glen-L Hot Rod build thread
Kane Custom Boats YouTube channel
Glen-L Boat Video Directory

Brad Tucker
Posts: 319
Joined: Tue Jun 29, 2010 7:20 am
Location: Washington, GA

Re: Tahoe 23 prop size?

Postby Brad Tucker » Tue Jul 11, 2017 10:03 am

I appreciate all the help. Paul, your spreadsheets are great. After thinking most of the night, I realized I had to add in weight for people and fuel. I used the spreadsheets to dial in numbers until the available HP most closely matched needed HP. If I did it correctly, it appears that a 12x15 or 12x14 will put me there, and give me 39-41 mph without going over the max HP available. 4000 lbs and 4600 lbs respectively. Unless I missed something. That's highly likely with me.

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Bill Edmundson
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Re: Tahoe 23 prop size?

Postby Bill Edmundson » Tue Jul 11, 2017 10:29 am

Brad

Did you add the Ice Chest? :lol:

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build


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