Correct prop size?

So.... numbers don't quite mesh.   PCM manual says the GT40 has a max rpm of 4800 and the 1995 CC brochures say the SN has a top speed around 46-47 MPH.   I've been noticing that my RPM's are somewhat high while cruising - at a comfortable 32-33 mph cruise and/ or ski speed the tach registers around 4000-4200. That doesn't give much room for getting anywhere close to 46 mph in the few hundred R's I have left. I haven't pushed it passed about 38-39 mph as yet, but at that the tach reads that I'm pushing 5200 or so.
Now first, I've always been very attentive to the engine and drive train with all my vehicles, boats included of course, and I'm fairly certain the engine isn't running at 5200 or even close - more like 4200 - 4400.    However that's still close enough to the top end that I have been wondering if the prop had been swapped out to a lower pitch at some point for some HD pulling power or something.    The other thing with CC's stated top speed is I can't find any info where it states which transmission ratio this is. They had 2 available: the 1/1   and the 1.23/1 - my SN is the latter.   Makes sense that if their #'s were from the 1/1 the top speed #'s for the 1.23/1 would be much lower.   So the question is how can I confirm that I have the correct prop for my transmission? If my ears are deceiving me and I really am cruising at that much higher RPM, I don't want to hurt my engine so I really want to get the correct prop. Checked the prop and the only markings on it were:

My 95 GT40 Pro Boss 310 HP Ski Nautique with an Acme 224 Prop will tack up to 52-5300 and will exceed 46 MPH.    32 MPH is taching more like 3400 RPM.
It used to pull 2-3 mph more but after an accident I had to have the prop straightened and it has not been the same since. Smooth and strong but I lost 2-3 MPH when the prop shop fixed my bent blade. I understand the Acme 422 is the most popular size for this boat but my 224 works really well also.

Good information, thanks to all. Funny, back in my I/O days I was a bit of a prop guru.... but the direct drive arena is a whole different ball game and I'm a little blind here.   

From what I've read already thanks to all of your google-fu suggestions, I've come to the conclusion that my prop, whether the pitch is ok or not, has got to go. So many posts talk about the old cast vs the newer CNC, specifically the consistency of the pitch and the balance of any individual blade. This is an area that I had never even considered as I had no idea the older props were cast - I had been used to dealing with props that were forged and balanced.   Ever since my first test drive I had noticed a slight, almost undetectable vibration that seemed to intensify the higher the rpm. I was hoping it wasn't a bearing somewhere, and all inspections seemed to confirm that as well. The prop imbalance would definitely account for this.

On another note, MrMcD's comment has me a bit confused...

MrMcD wrote: ... I understand the Acme 422 is the most popular size for this boat but my 224 works really well also.

In researching these two props, the 422 specifically states it has a 1" bore and the 224 says 1   1/8" -   Different bores available for different shafts? Adapters?

gt40KS wrote: I had no idea the older props were cast - I had been used to dealing with props that were forged

Fill me in.

I think it says OJ upside down and backwards, unless you rotate the prop then it will just say OJ

I started with the 14 / 16 OJ 4 blade and my spare was the 14/16 3 blade OJ.   Like you I was not happy with the RPM of my GT40 at 30 MPH and those props had noise at various speeds. Almost a howl type noise.   Switching to the Acme at Tim's advice was a solid move. My RPM at 30 MPH is around 3,200 now so cruise speed RPM is much better. Top speed improved a little and it pulls great out of the hole with no more noise at any RPM.
My shaft is a 1" shaft the prop is a 224.   I would like to try a 422 some day but have not purchased or borrowed one yet.   I bought my 224 from TIm specifically to lower my RPM at cruise speed and have been quite happy with it although due to an accident I had to rebuild it and it is not quite the same after the rebuild.

224 is 13x15.5, .090

TRBenj wrote: 224 is 13x15.5, .090

Guess I can't read too good today

PROPGUY wrote: Go with the 422 it is the best choice for this application. Some guys prefer a 654 or 668 but not most.

Thanks, that's by far the more popular recommendation and with more research the prop I'll end up getting. There's a few more little demons I have to chase in the ol' girl first, but the list is getting smaller all the time. With any luck I'll have the new prop on and be able to actually test it a few times before the dreaded cold sets in.

Then again, I have a nice selection of wetsuits......

The 224 wont change much, it is only .5 a inch bigger in diameter, but less cup. Your splitting hairs here. If you wanna lower the rpms a bit go to a 668 it has more cup. But it will only lower them about 50 rpm if you want more than that you have to add more pitch, you get about 300 rpm per inch of pitch. but more pich may hurt your off the line pulling.

I copied all the 1" RH props from the ACME site and put them in a spreadsheet to compare and filter if anyone's interested in looking at them.

I've been trying to figure out where to go with a prop on our 95 Ski as well. Currenly have a 1442 that needs a little refurb. We've ran the 654 and 1442. I have a 422 on our sport but I've never ran it on the ski. I like the 1442 numbers a lot but I'm not a 3-blade fan...still prefer the 4's I think.

ACME Prop Comparison Sheet with filters

Also, I think we're running 46-48 5k on the tach with the 1442. 13.25x15     0.090 cup 3 blade

The 654 has its place but it is not amongst my favorites for a HO NWZ. The expected use (all around, weighted for boarding, huge show ski loads, etc) plays a large part in prop selection, as does altitude. 422 and 224 are both good all-around options that should keep revs around 5000 at reasonable altitudes. Everything in the 15" pitch range will increase revs by ~200rpm, which is a little past the hp peak of a stock HO/GT40. The 1442/470/654 are good options if you either have a little more cam, or are willing to give up a little up top for some more low end pull. 4-blades should handle larger loads better if you're heavily weighted but the 3-blade Acme's are real, real close behind (and are more efficient up top). I do not care for the 668 on the NWZ hull but it could potentially be a decent option on a faster hull (like an '89). It does work well on the 6L 196's.

Anyone ever run this? 1490 13.25x15.5 0.060 cup

I love the bigger diameter that the 1442 has, I'd just like it with 4 blades better!

Bottom line is if you have a SN direct drive 1.23:1 trans the 422, 668 or 654 are the best options per Corrrct Craft and 1000s of correct craft owners promo guys tournament skiers etc its that simple.

644 and 536 are 1-1/8" props. Sounds like you have done a lot more testing, personally, than I have, PROPGUY.