Hi all, I'm not a new member but never posted here before.Some of you will recognize me from other forums as I continue on a restoration of a 1968 (hull #5) 23' Commander. As I near the completion of the mechanical phase I will soon be purchasing a prop. Originally the boat came with a 327F rated at 210Hp. I have had a new SBC built for this boat, A 350 warmed up to about 315Hp to stay within the safety guidelines of my V-drive's listed 300Hp rating. I have been in contact with Michigan Wheel and Acme and others for recommendations for diameter and pitch and cup, all of these resources have been very helpful but unfortunately they all conflict in small variants.For a baseline I thought it would be good information to know what prop this boat came with when equipped with the 427 which made an advertised 300Hp.

Does anyone know the diameter and pitch of the correct prop for this boat with the 427?

Many thanks,

Craig Wilson

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Did you ever run it with the 327F engine?  If so , did it make red line?  I ask because my 327Fs never got above ~3600 with factory props and gears.  With the 350's with some mods perhaps 275hp I achieved 4200.  Somewhere, probably in this forum I have seen a rule of thumb for hp/in of pitch. caveat rule of thumb doesn't rule out more than one thumb per hand.  Diameter is also one of those rules with clearance to hull which Greg Gajcak violated with great success. Dumb guess, +1"  diameter, +2" pitch.  Diameter can be reduced, pitch can be changed +/- 1"

Heluva first post, keep it up

Tim

I agree with Tim, if you have the original prop I would start there and see what it gets you. The original 327F had a red line of 4,000rpms. I’ve never been able to achive that with my factory props, 3,800 is the best I’ve done. Granted the engines have over 2,000hrs and the boat has gained a few pounds over the years. I think a 427 prop would be too much as the 427 will have alot more torque down low than a 350. 

Straight from the Club's Resource Collection 3.0  -----  14 x 14 x 1.25" for 427 powered 23 Commander. Clearly no reduction gear.

Thank you all for your interest and your suggestions.
I do have a prop that came with the boat but I found no markings on it for identification. Now that I found someone to talk to I can share my story and it definitely needs translation!
I found this boat about 7 years ago in a farm field in Holley, NY. I probably stopped and looked at it half a dozen times before I actually talked to the owner. Three years later I finally pulled the pin and bought it.
I was actually looking for an inboard Lancer and knew nothing about the 23 Commander but the more I dug and read the more excited I became about this boat, I mean there were only 115 of them made and I found #5!
I could not wait for the Mariner's Museum to re-open the Chris Craft vault so I could order an information packet, I received it in yesterday's mail. It might as well have been Christmas for a kid.
So I'm starting into my third year of restoration and have already done some of the most important things...interior gutted-all new floors, new engine beds, replacement of the shaft tube, all new wiring complete with electric distribution panel and 5000watt inverter, new interior side panels, new upholstery including construction of new "startrek" front seats and rear bench, conversion of the rear sundeck to open electrically, removal of all trim in preparation for paint, construction of a custom fit trailer and last but not least-a brand new not rebuilt Chevy 350 wolf in sheep's clothing.
This is going somewhere I promise,
so the prop mystery goes deeper than it should have because the engine I took out of the boat was not the original 327F. It turns out it was an automotive 350 transplant with unknown history, unknown hours and a marginal compression test so I opted to replace it and since the automotive rotation was opposite of the original engine it swung a left hand prop.
I never had the boat in the water to see how it performed since there was a Holley double pumper that was way too big for the engine and was all varnished-up and even after a rebuild would not idle as well as having a totally inappropriate single plane intake manifold that also had to go.
So I started from scratch with an opposite rotation 350, took it to my favorite machine shop and they proceeded to install a different cam, heads, MSD ignition, an Edelbrock Air-Gap intake and an Edelbrock 600CFM marine carb which when assembled and put on the dyno produces 317Hp. I will get out the dyno report tomorrow and let you know where the peak Hp and torque are.
So you can see that the prop that came with the boat is of no use other than scrap.
Tim and Mike, thank you for your help and Dick, the archived prop info you provided was just what I wanted to know. Another interesting point, your information confirmed that the boat came with a 1-1/4" shaft. Everyone that I talked to questioned me about that, apparently they felt that was excessive for the application.
Mike, you are most likely correct about the torque difference in the two engines, again-I know what my engine is rated for in torque and where it peaks, I don't have that information about the 427 to compare, anyone have that info?
If there is any interest I will post pix of the restoration thus far.

Craig

Craig, check the files for any "stuff" you might want to find, it probably is hidden there.  Torque for 427 look here https://tinyurl.com/427manual may need to scroll a few pages.

Ok, my Hp rating is 313.6 @ 5000 rpm compared to the 427's 300hp @ 4000, and my torque is 362.8 @ 3600 compared to 435 @ 2900.

I do believe the difference in torque from the small block to the big block will definitely affect my prop choice so really I'm back to square one not knowing what size prop I need. All the recommendations I got were for a smaller prop than spec'd for the original application with a hundred hp less. These are the various numbers I got from several sources; 13X10.5, 13X11.5, 12X14.6, 12X13.5, 12X12, 12X11.7 and 12X11.

I'm confused and props are too expensive for me to just start buying and trying.

Craig Wilson

Did you give them 5,000rpm as your wide open throttle number? If so this is why they’re giving you smaller props than original. The 327F while only rated at 210hp, it did it at just 4,000rpm and put out 300ftlbs of torque at 2,800rpm. I betif you wind a 327F up to 5,000rpm you’d be somewhere around 275hp.

What will probably help them lock down a closer prop number is knowing the boat original HP (210), wot (4,000), and top speed at wot, the last one I don’t know. 


Craig Wilson said:

Ok, my Hp rating is 313.6 @ 5000 rpm compared to the 427's 300hp @ 4000, and my torque is 362.8 @ 3600 compared to 435 @ 2900.

I do believe the difference in torque from the small block to the big block will definitely affect my prop choice so really I'm back to square one not knowing what size prop I need. All the recommendations I got were for a smaller prop than spec'd for the original application with a hundred hp less. These are the various numbers I got from several sources; 13X10.5, 13X11.5, 12X14.6, 12X13.5, 12X12, 12X11.7 and 12X11.

I'm confused and props are too expensive for me to just start buying and trying.

Craig Wilson

Considering prop sizing for your boat, let’s think way outside the box. Instead of thinking of your new engine as a baby 427, let’s think of it as a really healthy 327.  We know from experience that Chris-Craft was pretty good at sizing propellers for their boats. Chris-Craft originally supplied your 327 boat with  a 13 x 12 propeller and when they went to the 427 engine they went to a 14 x 14 propeller. We are going to have to spin your propeller pretty fast to get you up in your horsepower range so let’s not increase the diameter from their original suggestion on your boat of a 13 inch propeller. Let’s take the 327 engine prop spec of 13 x 12 and add a couple of inches to the pitch for a 13 x 14. Of the other prop recommendations you have received, I only like the 13 x 11.5' It is very close to what my martini fogged brain sez (or thinks) and could be repitched to 14"  I would also like to see cupping on the trailing edges of the prop. Cupping is usually worth an additional 1/2 to 1' of pitch, and reduces cavitation and related vibration at high prop speeds we hope to acquire,Remember, a good prop shop can easily reconfigure both pitch & diameter on these small bronze props. It's when they get bigger than 20" that they have to use heat and hydraulic presses to repitch. SOooooo ---- I'd cross my fingers and anything else on my body that I could get crossed and purchase a used prop to serve as a trial prop, knowing full well it will probably spend some time in the prop shop. Look what I found on Ebay, I hope your Q -V-Drive combo uses RH props.
 
Remember, this is a cheap test prop. I wouldn't be surprised if you wind up with a 13 x 13 with cupped blades. OK, its now 7 AM, time for my second cup of coffee and then shower, both of which are required to get my brain to maximum clarity when "Wild Ass Guessing Prop Sizes"  

Dick,

Thank you very much for your insight and suggestions. It's evident you have some experience in this field.

We are definitely thinking a parallel line.

I have a few more calls to make, I think I like the Acme prop best so far because they have an aft skew blade orientation which is supposed to give some stern lift reducing the need for trim tabs.

With all of the info I have gathered I think I will be looking at a 13X13 or 13X14 both with a heavy cup.

The link you provided was much appreciated but that prop was a 3/4" bore and we have no competent prop shops anywhere near where I live, even my favorite shop in Clayton is no-more so I am hoping I can obtain the correct prop on the first round as I have nobody that can do re-work.

Craig

I found out something interesting, since this post I received my info from the museum and the hull card for my boat states that it was equipped with a Federal Super Cup 13X13X1.25. Just more things to make me say hmmmmmmm!

Dick Morland said:

Straight from the Club's Resource Collection 3.0  -----  14 x 14 x 1.25" for 427 powered 23 Commander. Clearly no reduction gear.

If you're considering Acme, talk to Jim Thelen (Sales Engineer) at Acme, he helped me select the right prop for my boat. His phone is 888 661 2263

Thanks Jim,

I spoke with him several months ago and was thoroughly impressed with his knowledge. He was the one that brought up the subject of aft oriented blade rake which Acme does but no one else has mentioned  or that that technology even exists and for what purpose.

Now that I have my dyno results on the new engine I can call him back and let him decide what I need.

I find it very interesting that the prop that my boat came from the factory with differs from what is posted above in Dick's excerpt from the resource collection. I really love going back in time with whatever old information is available!

Craig

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