Nautique newbie - prop questions

[TRBenj]

It sounds like you may be looking for a softer "pull" rather than a softer wake/rooster? Thats an important distinction.

I guess the real question is whether the 422 was an improvement over the stock 14x16 in that regard. If it was, then theres a chance that going to an even shorter prop (like the 3-blade 470) might improve things. Though, my understanding was that shorter props that increase RPM's at skiing speeds would provide a "firmer" pull since they will hold speed a little better and cant be slowed down as easily with a strong pull from a skier. Of course, they shouldnt need to catch up if theyre not getting pulled down either... so I can see that argument too.

Honestly, Im not a good enough slalom skier to notice the difference of subtle prop changes like that... so perhaps someone else can weigh in on the topic.

Im sure you have already played with the Stargazer settings that would have an impact on the pulls firmness?

[Mikeski]

Have you considered going back to the factory OJ Legend 14 x 16 3 blade? It was the prop designed for that boat and I feel it's a reasonable choice as did the factory.

[HS]

So is it the pitch of the prop that makes the rooster tail? When we load up for surfing, with a 645 (13.25 " dia. x 16" pitch, cup of .105") there is a pretty big rooster tail. Would this be improved if we went with a larger diameter, and shorter pitch, like the 1273 (14.5" dia. X 14.25" pitch with .150" cup)?

[TRBenj]

So is it the pitch of the prop that makes the rooster tail? When we load up for surfing, with a 645 (13.25 " dia. x 16" pitch, cup of .105") there is a pretty big rooster tail. Would this be improved if we went with a larger diameter, and shorter pitch, like the 1273 (14.5" dia. X 14.25" pitch with .150" cup)?

No, I would say that the pitch of the prop will have an effect on the firmness of the rooster. Lower pitch = more revs = harder rooster.

I am not certain, but I would not be surprised if prop diameter had an effect on the rooster size... bigger diameter = bigger rooster? Diameter will also have an effect on RPM's (bigger diameter = fewer revs) but not nearly as big an effect as a change in pitch.

[Wac]

Have you considered going back to the factory OJ Legend 14 x 16 3 blade? It was the prop designed for that boat and I feel it's a reasonable choice as did the factory.

It has been reconditioned and isn't in the best of shape. The hope is that with all the CNC improvements in manufacturing that were not used when the original prop was picked for the boat, that maybe there is a better choice out there now. I know the boat is old, but it's in great shape so a new prop might be like new tires on an old car.

[TRBenj]

I think you are absolutely right. I tried the 13x16 OJ Legend 4-blade that came with my '90 after running the Acme's for a while and the difference is night and day. The difference in smoothness, acceleration, bite and top end were all very noticeable.

[Wac]

below is a series of email from Jim @ acme.... He was SUPER HELPFUL on this topic! The bottom line is I am going to send my prop in to them, have them add some cup to it to lower the RPM about 200 rpm... and see how my 422 turned into a 668 works for my application. (If you want to read through the below emails - start at the bottom and finish at the top)

THANKS to everyone who helped here, especially TRBenj and THANKS to the guys at ACME!!! I love good honest customer support!!

I will report back once i get a chance to test the new set up.



On Wednesday, September 28, 2011, Jim Thelen wrote:
> Yes, John, I think you are on the right track.
> Higher RPMs will generally translate into a stronger pull. Lower RPMs will generally translate into a softer pull.
> Regardless of*slight differences in horsepower, and assuming an engine in good*running condition,*the older boats with the carbureted engines*(4200 to 4600 OR 4000 to 4400 WOT)*are generally able to turn a little more propeller than the newer boats with the*fuel injected engines (4600 to 5000 OR 4800 to 5200 WOT).... Some of that might be due to RPM ratings and torque curves for the engines. Some of it might be due simply to carbureted vs. fuel injected.
> I don't really think 3 Blade vs. 4-Blade is too*big deal, at least concerning the Acme props... For your boat, with a 1.23:1 gear, I think it's pretty much a wash in terms of 3 Bld vs. 4 Bld... Both our 3-Bld & our 4-Bld props, for your boat,*perform very well, and both*seem to be relatively equal in*popularity,*once*we get the RPMs where*the customer*wants them, and in the range that they should be in. But every user is a little different --- some like a stronger pull, some like a softer pull --- everyone seems to have slightly different tastes in performance... And it is a general rule that when you slow down the propeller, the wake for skiing should improve, at least slightly. But the interaction of the hull design, with the propeller, has an impact on the results also.
> *
> For reference, if you were looking for a new prop, then based on our communication, I would certainly recommend one of the following propellers:
> 1. Acme # 668 - 12.50 X 15.50 VR4B 1.00 .150
> 2. Acme # 2068 - 12.50 X 15.00 VR3B 1.00 .150
> 3. Acme # 1442 - 13.25 X 15.00 VR3B 1.00 .090
> The 668 is simply the 422 with added cup. (The prop you are requesting)
> The 2068 and/or the 1442 might require a little more cup (added) for your tastes in pull and wake, but*these would be the 3-Bld props to consider, and/or test, for you and your boat.*
> *
> As for the time being, I do believe the best approach is to add cup to your current 422.
> And it should do the job just fine.
> And yes, it is a good idea for you to go out and get your actual WOT RPMs with your current 422 and let us know...*When you do so, the boat should be loaded*either slightly on the heavy side, or how you normally / generally use it, to mimic your standard use of the boat (e.g., 3/4 to full fuel,*and close to the typical number of people that you run in the boat).**
> Then we can make the calculation of exactly how much cup would be best, without overloading your engine.
> *
> One other thing: It might be a good idea to verify the RPM rating of your engine. There should be a tag on the engine that gives you a range, or gives you the maximum -- the engine is the best place to verify what the WOT RPMs should be.
> You indicated 4400. If this is max. ---- 4400, then your WOT range for the engine is typically considered to be 4000 - 4400.
> *
> Thank you,
> *
> Jim Thelen
> *
> www.acmemarine.com
> E: jthelen@acmemarine.com
> PH: 888-661-2263* or (231) 592-8711
> FX: (231) 592-0471**
> *
> ________________________________
> From: John Wacker [mailto:johnwackerjr@gmail.com]
> Sent: Tuesday, September 27, 2011 10:15 PM
> To: Bill Weeks
> Cc: Jim Thelen
> Subject: Re: ACME Marine Group Contact Form
>
> Jim,
> super helpful thanks!!! *The 4400 RPM i quoted you was what I understood to be the recommended WOT... I'm not sure what my actual WOT is with the 422 i have on there. * I didn't understand that the WOT is part of the calculation process. *Let me get a reading on my actual WOT and we can go from there. *
>
> If *i remember correclty, when i put the 422 on there several years ago, my RPMs for 34 mph went up about 200+\- * and the wake crossings felt much firmer than with the 14x16 OEM 3 blade that was on there. * However, the boat didn't lose as much RPM when a skier would pull against the boat in the wake crossings. *I went to the 422 because it was standard equipment *on the new more powerful engines in the nautiques, and i figured it might ski more like those boats. *It ended up being a firmer pull than those boats.... not sure why... unless my engine puts out more power than it should - which i doubt after 800 hours on the heads that are on there. * My guess now is that the extra RPMs and the extra blade ont he 422 compared to the OEM 3 blade is the reason... does this sound accurate???
>
> If you think I am headed in the wrong direction, please say so! *I originally thought a 3 blade acme would be the way to go, but I would love to hear your thoughts.... I didn't see one that was similar in size to the OEM prop so I thought of lowering the RPMs first on this one with more cup. *Are there any other effects of the more cup that I might expect? *Will it make the boat lean to one side more than where it is now? *I know that happened also when I switched to the 422, I had to put weight on the drivers side to keep it level with only the driver. *Again I attributed that to the 4 instead of 3 blades.
>
> I would rather dial in this prop on my old boat than get a new boat!! I'm too poor and my old boat is in GREAT shape!!
> Thanks,
> John
>
>
> On Tuesday, September 27, 2011, Bill Weeks wrote:
>> Hi John,
>> *
>> Your current prop --- Acme # 422 has .105 Cup currently (assuming it has not been repaired / modified)
>> *
>> Acme # 422 - 12.50 X 15.50 VR4B 1.00 .105
>> *
>> Based on your indications, recommendation would be to add .045 cup for an RPM reduction at WOT of about 200.
>> (Adding more than .045 cup would not be recommended, because of the requirements of your engine, and the possibility of it affecting other areas of performance not intended or desired.)
>> *
>> However, your indication of 4400 RPMs WOT is pretty much perfect for a 351 engine, and adding cup will lower those RPMs which could cause you to lose a slight amount of the hole shot / acceleration that you have now --- i.e., lower RPMs will typically translate into less hole shot / acceleration.
>> In this consideration, you may want to opt for an addition of .030 cup, which should only lower your WOT RPMs by approx. 120... and your WOT RPMs would then be at about 4280. (Note: For your engine it is not recommended to prop it at less than 4200 RPMs WOT)
>> *
>> Cost to add the cup: $50
>> *
>> If you would like to send your 422 into us to have us add the cup, please*call us at the toll free number below for a repair / return number, and also*so that we can be sure we have all the necessary contact and billing information for you on file and up-to-date.
>>
>> Please let me know if you have any other questions or concerns.
>>
>> Thank You,
>>
>> *
>>
>> Jim Thelen
>>
>>
>>
>> Sales Engineer
>>
>> jthelen@acmemarine.com
>>
>> ph. 1 888 661 2263*