Correct prop size? |
Post Reply | Page 123> |
Author | |
gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 946 |
Post Options
Thanks(0)
Posted: August-27-2017 at 4:01am |
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: |
|
JCCI
1995 Ski Nautique GT40 |
|
8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
Post Options
Thanks(0)
|
Joseph,
Are your RPM numbers from the dash or a shop tach? If just the dash, I suggest confirming them with a shop tach. Next, what is the dia. and pitch of the OJ? The picture of the prop shows the manufacturing date. The dia. and pitch are typically stamped in the hub under the prop shaft nut. Also, be aware that 1:1 and 1.23:1 trans's will have different props. |
|
MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
Post Options
Thanks(0)
|
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. |
|
KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
Post Options
Thanks(0)
|
Here's some reading for you in the link to a thread on props for a 96 SN
link After you pull your nut off the prop shaft, you'll find that it's a 14 dia by 16 pitch most likely, with your 1.23 to 1 transmission The 1 to 1 transmission boats typically came with a 13 by 13 prop and when the 1.23 to 1 came along more diameter and pitch was needed due to the slower turning propshaft which had let's say 23% more torque due to the gear reduction. So the 14 by 16 kept the engine in it's proper operating range, you got some extra pulling power and the same top speed. In the link you'll find reference to the 14 by 16 stock prop and suggestions for an ACME prop or 2 or 3.or 4 to replace it Read the post by TRBenj that's 4 posts down in the link I could try to write stuff for an hour and make this the longest post ever, but instead I'll just recommend doing a search here on CCF on props. Easiest way is Google just type in " Correctcraftfan 95 SN props" and you'll come up with enough prop related reading to keep you busy for a day or 2 Sounds like your tach isn't right or somebody put a lower pitch prop on it. If you have a newer digital timing light with a tach feature you could use the tach on that to check your RPM's . If you don't have one you should think about getting one, they're pretty handy So going back to what Pete said, pull your nut off and see what is stamped there for diameter and pitch as a starting point. |
|
gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 946 |
Post Options
Thanks(0)
|
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...
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? |
|
JCCI
1995 Ski Nautique GT40 |
|
KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
Post Options
Thanks(0)
|
Just so you know, the new CNC stuff from Acme and OJ is cast.
Here's a link to some Acme info from their site link |
|
8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
Post Options
Thanks(0)
|
Fill me in. |
|
gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 946 |
Post Options
Thanks(0)
|
Removed the prop nut, and as suspected it is stamped 14 16 cup ...
But then there is this mystery mark (bottom right) that I can't quite make out and not sure what it would mean anyway. |
|
JCCI
1995 Ski Nautique GT40 |
|
KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
Post Options
Thanks(0)
|
I think it says OJ upside down and backwards, unless you rotate the prop then it will just say OJ
|
|
8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
Post Options
Thanks(0)
|
Joseph,
I agree with Ken that the marking looks like "OJ". What props have you been dealing with that are forged? Big ones? |
|
MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
Post Options
Thanks(0)
|
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. |
|
KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
Post Options
Thanks(0)
|
I'm not sure where you're researching but the Acme website lists both the 422 and 224 as RH props for a 1 inch shaft. Here's a link to their ski boat prop page link 422 4 blades 12.5 by 15.5 RH with .105 cup 224 4 blades 13 by 15 RH with .090 cup |
|
TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
Post Options
Thanks(0)
|
224 is 13x15.5, .090
|
|
gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 946 |
Post Options
Thanks(0)
|
[/QUOTE]
I'm not sure where you're researching but the Acme website lists both the 422 and 224 as RH props for a 1 inch shaft.[/QUOTE] Yeah, typo. Pulled up the history and it seems I typed in 2247 in the search |
|
JCCI
1995 Ski Nautique GT40 |
|
KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
Post Options
Thanks(0)
|
Guess I can't read too good today |
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(0)
|
Go with the 422 it is the best choice for this application. Some guys prefer a 654 or 668 but not most.
|
|
gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 946 |
Post Options
Thanks(0)
|
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...... |
|
JCCI
1995 Ski Nautique GT40 |
|
MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
Post Options
Thanks(0)
|
Tim, do you remember how the 224 and 422 compared? I do know most lean toward the 422 option but I don't remember why. I think the 224 hit my desire to lower the RPM at cruise speed a little better than the 422 option.
|
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(0)
|
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.
|
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(0)
|
MrMcD, You still using the 224? I can rebuild it for you to Acme specs. or Ill buy it from you if your not happy and want a 422. I think I have heard the larger diameter of the 224 makes a bigger rooster and hardens the wake.
|
|
mdvalant
Grand Poobah Joined: May-06-2009 Location: Bellevue, IA Status: Offline Points: 2059 |
Post Options
Thanks(0)
|
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 |
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(0)
|
Mdvslant, The 422 or the 654 are the two best options for your boat right Chris Jemic?
|
|
TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
Post Options
Thanks(1)
|
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.
|
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(1)
|
The 654 will perform almost identical to the 422 but with a half inch less pitch the rpms will be about 150 higher, some say the wake shape is different also. The complaint on the 224 is the wake also, its larger diameter changes the wake and makes a larger rooster. This is for ski boats only heavily weighted or wake boat prop selection is totally different. Transmission ratios change for wake boats and vdrives so whole different ball game. Three blades run better on 1:1 transmissions, 4 blades run better on reduction transmissions as a general rule.
PS a 668 which was designed for a 6.2L will work also, it will just drag your rpm down another 100. it can be recuped to be a 422. |
|
mdvalant
Grand Poobah Joined: May-06-2009 Location: Bellevue, IA Status: Offline Points: 2059 |
Post Options
Thanks(0)
|
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! |
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(0)
|
Go with a 1490 13.25x15.5 then, its a 4 blade.... I have a few 644s 13.25x16, or 536s 13.5x16 popular wakeboard props.
|
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(0)
|
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.
|
|
MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3734 |
Post Options
Thanks(0)
|
I am still running the 224 and pretty happy with it. I have been skiing at only 15 off lately and I don't think that will change in my future so the wake has been fine and zero prop wash issues. If I could go 39 off I might be concerned. The best part of the change to the Acme 4 blade was the elimination of noise we had with the OJ. The boat will accelerate hard enough to pull my arms out. I don't think we ever use more than 1/4 throttle to pull a deep water start. I am curious what I would see different with the 422 prop but I am happy with the 224, the RPM at wide open will hit 5200-5300 at 1,200 ft elevation depending on how much load is on board.
|
|
TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
Post Options
Thanks(0)
|
644 and 536 are 1-1/8" props. Sounds like you have done a lot more testing, personally, than I have, PROPGUY.
|
|
PROPGUY
Newbie Joined: November-22-2016 Location: Florida Status: Offline Points: 37 |
Post Options
Thanks(0)
|
Yes the 536 and 644 are for the wake board boats...I dont do much testing I have just been dealing with Nautique on props gor years, I even have prototype props here that dont exist.
|
|
Post Reply | Page 123> |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |