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PostPosted: Fri May 25, 2012 9:03 pm 
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Joined: Tue Oct 20, 2009 12:23 pm
Posts: 11
Location: Reno, Nevada
I am just about ready to launch my Monte Carlo (pictures to follow after it is washed and waxed this weekend) but I am in need of a prop size. I am running a PCM ZR6 at 375 HP. Does anyone have an idea where I can start with a prop size? I have a friend who owns a boat shop and will let me try several sizes before I buy, but I would like to start out pretty close. Any ideas?

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Dave Solaro
Monte Carlo - Mercoledi
Reno, NV


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PostPosted: Sat May 26, 2012 12:26 am 
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Joined: Wed Feb 17, 2010 5:42 pm
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Location: Sunshine Coast, Queensland, Australia. Building Gentry.
Hi Dave. Well done getting this far. Not quite enough info for us to help yet though, (bearing in mind that I am no expert).
What is the maximum prop diameter you can fit?
Any reduction in the transmission?
What is max engine RPM?

My 5.7L 325HP Small block has a recommended starting place of 12 x 14 or maybe 12 x 15 with no reduction and max RPM 5500. My guess for you would be 13 x 14 or 13 x 15 but there is also cupping to consider.

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PostPosted: Sat May 26, 2012 4:44 am 
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Joined: Sat Jul 04, 2009 3:50 pm
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Location: Branson, MO
Ok, Dave - need to know - are you straight drive or do you have the down angle reduction transmission PCM mates with these engines.

I can tell you that you will need some meat for a prop. I have the PCM 343HP and had to go to a 13.5x16 four blade overcupped to .130 just to keep the engine within RPM tolerances. I originally had a 13x16 three blade. The engine would exceed rpm tolerances in a blink of any eye. I went over 7000 RPM a couple of times with that blade.

So I expect you will have to start with something like the 13.5x16 four blade. What is your drop on your strut?

dave

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PostPosted: Sat May 26, 2012 4:44 am 
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Joined: Sat Jul 04, 2009 3:50 pm
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Location: Branson, MO
Ok, Dave - need to know - are you straight drive or do you have the down angle reduction transmission PCM mates with these engines.

I can tell you that you will need some meat for a prop. I have the PCM 343HP and had to go to a 13.5x16 four blade overcupped to .130 just to keep the engine within RPM tolerances. I originally had a 13x16 three blade. The engine would exceed rpm tolerances in a blink of any eye. I went over 7000 RPM a couple of times with that blade.

So I expect you will have to start with something like the 13.5x16 four blade. What is your drop on your strut?

dave

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My Riviera build - the Midnight Cry Project

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Few things in the world measure up to the thrill and satisfaction of boating in a boat that you built.


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PostPosted: Sat May 26, 2012 7:55 pm 
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Joined: Tue Oct 20, 2009 12:23 pm
Posts: 11
Location: Reno, Nevada
I am using the PCM 1.23:1 down angle transmission. The manual indicates that the max RPM is 5300 with 5200 being preferred. I used a 16 degree 7 1/2" drop strut which should give me plenty of room for a 14" prop if needed. I appreciate the help, and as soon as the weather clears up this weekend I will get some pictures to show her off.

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Dave Solaro
Monte Carlo - Mercoledi
Reno, NV


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PostPosted: Sun May 27, 2012 3:34 am 
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Location: Branson, MO
You have the exact same setup I have. A 14" prop will be too big. The recommended clearance between the prop and keel is 2". I am closer than that right now. I thought of going to 14" but it would put me right at 1" of the hull and I worried about prop wash damage

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My Riviera build - the Midnight Cry Project

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Few things in the world measure up to the thrill and satisfaction of boating in a boat that you built.


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PostPosted: Sun May 27, 2012 8:14 am 
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Joined: Tue Oct 20, 2009 12:23 pm
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Location: Reno, Nevada
Thanks Dave. I will keep that in mind when I start out with the sizing.

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Dave Solaro
Monte Carlo - Mercoledi
Reno, NV


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