Prop thoughts.

[inair]

So, I talked to some one at Nettles Props. The guy seemed in a bit of a hurry, it was late on a Fri afternoon. His recommendation was ACME 1792 four blade. On Monday I called Skidim to talk to the folks there about the 1792 because they have always been Very helpful. He couldn't figure out why the 1792 would be advised for my boat but gave a strong recommendation for the Acme 422. I then called Nettles back and talked to Jim. He said the 422 is good but the 668 is better. Same diameter and pitch but with cup added. I ended up ordering an Acme 668. Any body else out there running this on 230hp 1:123 Sunsport? I mostly ski, the kids board and I have about 800# of ballast that I use for that.

I guess I'm a little uneasy because I did a search on here and there really is allot of variation to these boats and how they are used. Add to that some dealer advise that put me off a little. Any way, new prop is on the way and my fingers are crossed!:confused:

[TitanTn]

This is certainly a subjective type of subject, but I would feel confident in what Jim suggested. I'm guessing you'll be very pleased with the performance of your new prop, but let us know for sure when you come up for the Southern Supra Reunion!

[inair]

I like it....."a subjective kind of subject":) And by the time the reunion comes around I should have a good amount of lake time on it and be able to give you all the scoop.

[jsta281]

What is the pitch on you current prop? The 668 sounds like alot of pitch for 230 hp. I run a 668 on my 409 hp 1.23 trans ski nautique. When I buy a new prop or a 2nd prop for spare I will be looking at less pitch possibly a 422 or even 470 (3 blade)

The Acme 1792 Propeller 4 Blade 13.5 x 14.25 RH 1" Bore .105 Cup

Here are the dimensions for the acme props near 668

Props

668-- 12.5 - 15.5 -- .15 (4 blade)
654 --12.5 -15.0 -- .105 (4 blade)
422 -- 12.5. -15.5 -- .105 (4 blade)
470 -- 12.5 - 15.0 -- .105 (3 blade)
224 -- 13 - 15.5 -- .09 (4 blade)

.5 in pitch will change RPM about 200. Reducing pitch will increase RPM.

The 1792 although bigger in diameter has alot less pitch which will not propel the boat as far forward per rpm helping with hole shot and getting to higher rpm quicker where you boat makes more power.

Frankly I don't see the 1792 prop even being in the "similar" category as a 668 and I think the 668 is way to much pitch for your power.

Again What are the current specs of you current prop and what is it you want to change most about the pull from your boat?

[inair]

jsta281, that is a lot of info to digest there. Since my current prop is not the one that came with the boat and I don't know what it did come with, and the one I have now bogs, is hard to keep on speed and is the source (I think) of a vibration even after I had it worked on, I need to find some workable alternative. My current prop is an OJ 14/15. When talking to Jim, he said that the 668 is essentially a 422 with more cup and that for the direct drive 230hp 1:123 transmission, it would be a good choice. Without any real knowledge or experience with the info you provided, I admit, I don't know what to think. I guess thats why I started this thread, too see what others experiences are.

Thanks for your input.

[jsta281]

If your current problem is a 15 pitch And your motor Boggs Going to more pitch Seems to me is only going to make it worse. More cup in the 668 over the 422 is also going to make "bogging" more prevalent More cup grips the water more.

I am not a prop specialist. However I have done a lot of research and discussing props for my boat with people who do know what they're talking about.

I'm going to send you a PM.

[inair]

Well, I learned a little more about the prop situation over the week-end. I had the carb rebuilt and it seems that the secondaries may have been the issue I had with "bogging" and not making Spec WOT RPM.

The next thing I learned is that Supra installed more than one prop on these boats. My current Prop, which I've been told is past its service life, is an OJ 14x15. Even if this is not the original prop for my boat, it is very close because there are 1991 Sunsports with the 351 engine and reduction tranny that did come from the factory with that prop.

The next thing is that smaller diameter props have less mass and spin up faster equaling a slightly better hole shot, but they sacrifice top end. So since I'm already slinging a 14 incher I thought I would start there and look down through all ACMEs props for something in the 12.5 to fifteen pitch, one inch bore and R rotation just to see what was there.

I then learned that 3 blades are more efficient and faster than four, all other things being equal. The only thing that 4 blades do better than three is that its easier to balance them, so there may be slightly less vibration. So three blades was added to the list.

Well there are no Acme 14 inch three blade props in close to the right pitch range and the following are as close as I could come.

470 12.5x15
1458 13x14.8 with .8 cup
1442 13.25x15 with .09 cup

The only real question I have left is: what is the actual effect of the larger blade size on all this in terms of making the boat turn 4400rpms at WOT? So I will make a few more calls tomorrow and let you know what I find.

Thanks jsta281 for pointing me toward some real knowledge on this.

Ken

[jsta281]

Well I'm not sure I offered a lot of correct advice but if it got you pointed in the right direction great.

A couple questions

what is the reduction ratio of your trans?

What motor?

[inair]

Motor is 351 Ford PCM 230HP. Trans is 1.23:1

[jsta281]

What is the primary use of this boat? Skiing or wakeboarding?

I would guess that of all the props you listed the 470 3 blade would be the best option to increase top end and ski characteristics? The smaller diameter would also help ski characteristics. In my mind the remaining question for a "ski first" application is if it is to much pitch?

Also, I would question if the boat did come with a 14 in dia prop originally. With that said if you want a "wakeboard" first application the larger diameter prop may have more benefit. Again the only question would be if less pitch might improve both hole shot and possibly top end speed.

What is the max rpm you see when the boat is running well with the 14x15 prop?

[jsta281]

Apparently 15-16 pitch props were common for that engine trans application. However, if your boat is struggling to reach max RPM when running well, a drop in pitch would help in that regard.

[kvand347]

Just going to throw this out there.

My boat is the 285hp version of yours Ken. The boat came to me with a 14x16 3-blade prop that was reduced to a 14x14 as a 14 was stamped over the 16. Hole shot when weighted with ~1,800lbs of ballast was mediocre at best. I can't remember what top speed was or the rpm's at that speed.

I have since upgraded to the Acme 422. Hole shot was much improved while weighted. Top speed increased by 2 mph. Keeping wakeboarding/ wake surfing speeds has been much easier. I still tend to hunt a little during wakeboarding, but wake surfing I can usually get it to stay at one speed without having to adjust throttle.

I wish I had exact numbers on rpm and speed, but I can assure you that it was a "kick in the pants" improvement. Before I bought the #422 I called both Nettles and Acme. They both gave me 2 different props that would work for my application. I think anything they suggest over stock is going to be a big improvement for you.

[jsta281]

Just going to throw this out there.

My boat is the 285hp version of yours Ken. The boat came to me with a 14x16 3-blade prop that was reduced to a 14x14 as a 14 was stamped over the 16. Hole shot when weighted with ~1,800lbs of ballast was mediocre at best. I can't remember what top speed was or the rpm's at that speed.

I have since upgraded to the Acme 422. Hole shot was much improved while weighted. Top speed increased by 2 mph. Keeping wakeboarding/ wake surfing speeds has been much easier. I still tend to hunt a little during wakeboarding, but wake surfing I can usually get it to stay at one speed without having to adjust throttle.

I wish I had exact numbers on rpm and speed, but I can assure you that it was a "kick in the pants" improvement. Before I bought the #422 I called both Nettles and Acme. They both gave me 2 different props that would work for my application. I think anything they suggest over stock is going to be a big improvement for you.

What top speed do you see now and what RPM?

The non HO 351 sweet spot is about 4400 RPM for top speed. I suspect your RPM may be 200-300 higher. It is critical becasue if your boat with more power does not get go above 4400 rpm when reaching top speed then it is unlikely that he will see 4400 rpm with the same prop. On the other hand if your boat zips right past 4400 rpm in to the 4600-4700 range then the 422 may work for him as well.

If you love your 422 and all things were equal between boats but the 45 extra hp your motor makes I would guess (and it is a guess without all the data) that the ACME 654 (Same prop as 422 with .5 less pitch) would be a great choice.

[kvand347]

What top speed do you see now and what RPM?

The non HO 351 sweet spot is about 4400 RPM for top speed. I suspect your RPM may be 200-300 higher. It is critical becasue if your boat with more power does not get go above 4400 rpm when reaching top speed then it is unlikely that he will see 4400 rpm with the same prop. On the other hand if your boat zips right past 4400 rpm in to the 4600-4700 range then the 422 may work for him as well.

If you love your 422 and all things were equal between boats but the 45 extra hp your motor makes I would guess (and it is a guess without all the data) that the ACME 654 (Same prop as 422 with .5 less pitch) would be a great choice.

Great questions and I wish I had solid info. I'm basing this off memory...

I want to say my RPM's hit 4600 and about 46 mph...

I'm pretty sure that my RPM's increased a little with the 422. Hole shot got better and top speed improved, too.

[jsta281]

That's right in line with what I would have guessed.

Based on that if I had to make an educated guess for the OP I would go with ACME 654 (4 blade) or 470 (3 blade) they are identical specs.

Even if the boat will run out on the top (push the RPMs beyond 4400 rpm at WOT) it would still help hole shot and slower speeds.

Either-way it seems that the 668 would likely be more pitch then necessary for optimal performance, assuming your boat and OP boat are the same less the HP difference.

[kvand347]

Sounds about right to me. Wouldn't it be nice to test all the props before choosing the right one for your application? I bought the #422 because it was a deal I couldn't pass up. It ended up making a big difference for wake boarding/surfing even if it wasn't the recommended prop per Nettles and Acme.

[jsta281]

Sounds about right to me. Wouldn't it be nice to test all the props before choosing the right one for your application? I bought the #422 because it was a deal I couldn't pass up. It ended up making a big difference for wake boarding/surfing even if it wasn't the recommended prop per Nettles and Acme.

If you are seeing the rpm range where max power is made at wot then you got the correct prop even if by "luck"

[skiman_61]

Back in the day I was an outboard guy. I spoke with a fellow at one of the larger prop makers, can't remember just what one now, OJ maybe? I was jonesing for a SS prop for my 140 Johnson. The manufacturer said that within certain parameters, number of blades and whatnot, it really made little difference. Sounds like you have some close choices for your boat. May be not much difference between them? What you running now?

[jsta281]

Back in the day I was an outboard guy. I spoke with a fellow at one of the larger prop makers, can't remember just what one now, OJ maybe? I was jonesing for a SS prop for my 140 Johnson. The manufacturer said that within certain parameters, number of blades and whatnot, it really made little difference. Sounds like you have some close choices for your boat. May be not much difference between them? What you running now?

I don't presume to know about I/O props but it seems that they maybe less finicky to maximize performance because you can manipulate the prop angle to Get more rpm

What I have come to understand by asking someone with much more experience is that for inboards top end speed is directly related to picking a prop with the most pitch that you can still achieve peak HP on the RPM curve. Falling short of optimal RPM is falling shirt of maximum top speed.

Some choose to sacrifice a small amount of top speed for better hole shot to do so you drop pitch. This however will raise your RPMs across the board at all speeds.

[SquamInboards]

Comparing to the old prop is tough, for several reasons: the old one is probably hand made, and therefore less precise. It could have been rebuilt or otherwise modified in its life, and its overall blade area (% of the overall area within a circle that is taken up with blades) is probably much less than a modern CNC Acme prop. My boat had an OJ 14x16 4 blade, hand made prop that had been rebuilt several times. The measured diameter was actually under 13" when I took it off. I put on an Acme 1868, smaller in every dimension except blade area - 12.5 x 14.25 4 blade .075 cup - and it turned almost exactly the same WOT RPM, although much more smoothly, and the overall feel and throttle response was much better. With a 310hp engine and a 1.23:1 transmission, a 422 seemed like the right prop on paper, but it was way under WOT by 400-600 RPM.

The only way to be 100% sure about getting the right one is to try it with your individual boat, using it the way you expect to normally use it. A lot of places will let you try a prop and exchange it, provided it comes back undamaged.

[kvand347]

Comparing to the old prop is tough, for several reasons: the old one is probably hand made, and therefore less precise. It could have been rebuilt or otherwise modified in its life, and its overall blade area (% of the overall area within a circle that is taken up with blades) is probably much less than a modern CNC Acme prop. My boat had an OJ 14x16 4 blade, hand made prop that had been rebuilt several times. The measured diameter was actually under 13" when I took it off. I put on an Acme 1868, smaller in every dimension except blade area - 12.5 x 14.25 4 blade .075 cup - and it turned almost exactly the same WOT RPM, although much more smoothly, and the overall feel and throttle response was much better. With a 310hp engine and a 1.23:1 transmission, a 422 seemed like the right prop on paper, but it was way under WOT by 400-600 RPM.

The only way to be 100% sure about getting the right one is to try it with your individual boat, using it the way you expect to normally use it. A lot of places will let you try a prop and exchange it, provided it comes back undamaged.

That's interesting! What is your WOT RPM's? What should it be for my boat? How do I know if I'm properly propped? :)

[Jetlink]

That's interesting! What is your WOT RPM's? What should it be for my boat? How do I know if I'm properly propped? :)

Not sure if it is stamped on your engine but I have a stamp of some sort on the left valve cover that has a bunch of pertinent engine information among other things is optimal and max RPM range as well as other information like spark plug gap and timing.

[kvand347]

Not sure if it is stamped on your engine but I have a stamp of some sort on the left valve cover that has a bunch of pertinent engine information among other things is optimal and max RPM range as well as other information like spark plug gap and timing.

Good call! I don't have anything stamped on my motor (maybe because it was rebuilt) but I do have the PCM manual and I'll have to check that tonight.

[jsta281]

Comparing to the old prop is tough, for several reasons: the old one is probably hand made, and therefore less precise. It could have been rebuilt or otherwise modified in its life, and its overall blade area (% of the overall area within a circle that is taken up with blades) is probably much less than a modern CNC Acme prop. My boat had an OJ 14x16 4 blade, hand made prop that had been rebuilt several times. The measured diameter was actually under 13" when I took it off. I put on an Acme 1868, smaller in every dimension except blade area - 12.5 x 14.25 4 blade .075 cup - and it turned almost exactly the same WOT RPM, although much more smoothly, and the overall feel and throttle response was much better. With a 310hp engine and a 1.23:1 transmission, a 422 seemed like the right prop on paper, but it was way under WOT by 400-600 RPM.

The only way to be 100% sure about getting the right one is to try it with your individual boat, using it the way you expect to normally use it. A lot of places will let you try a prop and exchange it, provided it comes back undamaged.

I concur with this exactly. And ACME equivalent to an old hand made is usually at least 1" drop in pitch.
An Acme 1868 may also be the right prop depending on how strong the OP's motor is running. If it is down on power at all 15" pitch could still be to much.

[SquamInboards]

On the old carbureted PCM / Ford 351 @ 240 hp, max WOT RPM was 4400. I have the GT-40 351 that ran from 1995 - 2001 or so, with a max RPM of 4800. I can only get up to 4800 with 1/4 tank of gas and only me in the boat. But max SUSTAINED recommended RPM is only like 3800, which I can easily turn with the 1868, even with lots of people / ballast.

Edit: looking at your signature, Kevin, I see you have the H.O. @285hp. Not sure the WOT RPM on that one, I can look it up though. Someone will probably beat me to it.

And to the power loss issue, we've had to put the 1868 on a boat that previously ran a 422, maybe it had some water weight, engine was tired, or a combination thereof. But it needed the drop to a 14.25" pitch to get up to 4800 RPM.

[inair]

Comparing to the old prop is tough, for several reasons: the old one is probably hand made, and therefore less precise. It could have been rebuilt or otherwise modified in its life, and its overall blade area (% of the overall area within a circle that is taken up with blades) is probably much less than a modern CNC Acme prop. My boat had an OJ 14x16 4 blade, hand made prop that had been rebuilt several times. The measured diameter was actually under 13" when I took it off. I put on an Acme 1868, smaller in every dimension except blade area - 12.5 x 14.25 4 blade .075 cup - and it turned almost exactly the same WOT RPM, although much more smoothly, and the overall feel and throttle response was much better. With a 310hp engine and a 1.23:1 transmission, a 422 seemed like the right prop on paper, but it was way under WOT by 400-600 RPM.

The only way to be 100% sure about getting the right one is to try it with your individual boat, using it the way you expect to normally use it. A lot of places will let you try a prop and exchange it, provided it comes back undamaged.

After all my talking to the folks at ACME, Skidim, and Nettles plus doing a bunch of reading, I think this is all true. Even after I did my own research and called ACME again to talk prop theory, he stuck to his original recommendation (422/668). There are so many variables that making a final definitive choice that fits everything perfectly is more art than science. ACME keeps a data base of what props are sold for what engine /boat combos. So after they do their own engineering, when someone tells them that a certain boat/motor/prop works well for some application, that is added to the data and can change what they recommend to someone who calls. So since they are so generous with their return policy, I will take the opportunity to run the boat with what they sent me for a bit and then make adjustments if necessary.

Geeez! Winter seems to be lasting a long time this year ;)

[jsta281]

Please return when spring finally gets here and give us an update. As a matter of a purely mental exercise I would like to know how it all turns out.

One other thing I think to keep in mind is when selecting a prop it's usually a matter of good better and best. When you put the 668 on compared to your old handmade prop I have little doubt that it will feel like a major improvement. If it feels great and you're happy with the performance then that's all that matters. However, the "best prop" will see your peak horsepower range on the RPM curve. If you don't see that RPM range then you're leaving performance on the table.

Definitely log your rpm's at various speeds. Log RPM and speed at surf speed and wakeboard speed skiing speed and cruising speed and Top Speed.

Also remember

.5 in pitch will change RPM about 200. Reducing pitch will increase RPM.

I look forward to seeing how it all shakes out.

[kvand347]

On the old carbureted PCM / Ford 351 @ 240 hp, max WOT RPM was 4400. I have the GT-40 351 that ran from 1995 - 2001 or so, with a max RPM of 4800. I can only get up to 4800 with 1/4 tank of gas and only me in the boat. But max SUSTAINED recommended RPM is only like 3800, which I can easily turn with the 1868, even with lots of people / ballast.

Edit: looking at your signature, Kevin, I see you have the H.O. @285hp. Not sure the WOT RPM on that one, I can look it up though. Someone will probably beat me to it.

And to the power loss issue, we've had to put the 1868 on a boat that previously ran a 422, maybe it had some water weight, engine was tired, or a combination thereof. But it needed the drop to a 14.25" pitch to get up to 4800 RPM.

Per PCM Manual for my boat: Max (Intermittant) RPM = 4400. Cruising is 3600. I may have to take a look in the spring to see if I am getting to 4600 or not.

[skiman_61]

Did you happen to speak with anyone from OJ? Just curious. I'm a skier as well. Some places will indeed let you try a prop and send it back. Let us know how it turns out?

[inair]

Skiman 61, I didn't talk to any one at OJ. But as to ski props.....well there is more to ski props than jsut the regular prop theory. From looking at other boards more oriented toward the ski crowd, some props put up more or less rooster and at varying distances from the back of the boat and to make it even more interesting speed plays a role as well. Some even said that other wake characteristics changed with certain props and everything can change from boat to boat. Seems like a lot to keep track of but trial and error mixed with some good advise and knowing what you are looking for in terms of WOP RPM and wake shape at speed you ski at will bring the best results.

I'll let everyone know how this all takes shape as we get into some warmer weather.