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BrianM
08-02-2009, 03:25 PM
Just got the chance to compare a couple of more props on my boat. Figured I would post up my findings here for all. Speeds and RPMs were confirmed via GPS and baseline RPMs were calibrated with Perfect Pass Stargazer. Hole shot and feel behind the boat was seat of the pant/ski observations. All testing at sea level. Your mileage may very.

Boat:

1997 Prostar 190 GM TBI 350 275hp 1:1

Props:

Acme 13x12 .80cup 3 blade (541)
OJ XMP 13x11.5 .90 cup 3 blade
OJ XMP 12.5x12 .90 cup 4 blade.

Prop Top Speed Max RPM 34mph 36mph
Acme 44.5 No Data 3150 3400
OJ 3 43.7 4490 3290 3500
OJ 4 42 4530 3370 3605

Smoothness:

All of these CNC'd props feel silky smooth inside the boat. No vibrations at any speed. The Acme has a bit of a growling sound when cutting the throttle from speed. The OJ 4 blade has a very distinct sound at all speeds which is quite different from either of the 3 blade props. The OJ 4 blade also kind of felt like you were hitting the brakes when cutting throttle from speed. The OJ 3 blade was just smooth with no other noticable sounds or feel inside the boat.

Top Speed:

The props fell into line just as one would expect on the top end speed. The Acme had the best top end of the three props with the OJ 3 blade just .8mph slower and then the OJ 4 blade nearly two mph slower still.

Hole Shot:

This is rated by me strictly seat of the pants. I did not time with a stop watch to a certain speed but I do have a relatively short setup lake that is driven the same way every time so it is pretty easy to see how quick the boat gets to speed and locks in speed on the PP in relation to the course. The OJ 3 blade was the prop to beat in terms of hole shot. This prop spun up very fast out of the hole and was up to either 34 or 36 mph long before the 55 meter buoys. The amount of throttle needed out of the hole to pull up the skier was a bit less than the Acme and substantially less than the OJ 4 blade. Overall the two 3 blade props felt the quickest out of the hole and required much less throttle to get to a set speed than the 4 blade. You can see the difference in the RPM chart at the top.

Pull in the Course:

The OJ 3 blade had the 'softest' pull of the bunch. Behind the boat the boat felt very foregiving while in the boat there was still very good speed holding ability. The OJ 3 blade in my mind just had a great pull.

The OJ 4 blade on the other hand had a much 'firmer' pull. Behind the boat it felt like you were being pulled by a freight train out of the ball. Not much give. In the boat there was great speed holding ability but you could really hear the additional RPM the engine was spinning to maintain the same speed.

The Acme falls somewhere between the two OJ props in terms of feel behind the boat. It is a little firmer than the OJ 3 blade and a bit softer than the OJ 4 blade.

Wake:

I have been running the Acme 541 on my boat for over 3 years now. While the wake profile was always very flat with nearly no rooster tail at slalom speeds I have always felt the wake was a bit on the hard side. The biggest reason for me testing a couple of other props was to see if I could find a softer wake. So for comparison I will use the Acme as a wake baseline.

The OJ 4 blade changed the wake characteristic quite a bit. I found the wake to be a bit narrower and just slightly taller than the Acme. There was more rooster tail at 34 and 36 mph. Overall the wake felt just a bit softer than the Acme but the rooster tail was noticable at 22 off. 28 off the rooster tail was gone.

The OJ 3 blade had a nearly identical wake profile to the Acme. The wake was lower and slightly wider than the OJ 4 blade with no rooster tail at any line length or speed. The OJ 3 blade also provided a substantially softer wake than the Acme. The rooster tail was now completely gone and in its place only soft bubbles.

Summary:

The OJ XMP 13x11.5 wins this prop comparison in my eyes. It is very fast out of the hole, provides a nice soft pull for the skier while still providing great speed holding ability in the course. This prop also managed to soften up the wake providing a very low buttery soft wake with no rooster tail at all line lengths. It gives you all of this while only having to give up .8 mph compared to the Acme on the top end speed.

Bottom line is I sold my trusty Acme 541 and am replacing it with the OJ XMP 13x11.5 3 blade. Overall this prop provides the best combination of characteristics for my boat and use.

If anyone has any specific questions about any of these props I would be glad to answer as best I can just ask them in this thread.

And for anyone still running an old 13x13 forged prop on your boat do yourself a favor and upgrade to one of the new CNC'd props. It will absolutely be the best upgrade you make on your boat. I had been running my spare stock prop the last few times out and putting on the CNCd props completely transforms the boat. Relegate those relics to 'spare' duty.

T-Rager
08-02-2009, 04:22 PM
Nice job, Brian. This is very useful information and I appreciate your efforts.

I have been running the Acme 541 on my 1990 ProStar for the last 5 years and am pleased with it. However, now I will have to give the OJ 3-blade a try.

OHIOPRO205
08-02-2009, 05:22 PM
Were did you purchase the prop? I have got a 94 205 with the same engine and tranny and I am still running the stock prop.

gibbons
08-02-2009, 05:34 PM
I got one of the very first OJ 4-blades way back when.... 96ish? I am still using it today. I have often wondered about a CNC prop, it's got to be more precision than the old ones. The problem is, when I bought the 4-blade, I sent it back to OJ for some tweaking to get a bit more RPM, maybe 200 more. I don't recall what they did. If I sent the prop to one of the manufacturers, could they read the cup and pitch to recommend one of their off-the-shelf units?

ttu
08-02-2009, 06:03 PM
now load that boat down with 2000lbs of ballast and give us a prop comparison.:rolleyes:

just kidding, great write up brian!

TallRedRider
08-02-2009, 07:00 PM
I have never been able to understand how the prop changes the wake characteristics. I know many of us believe the prop somehow makes a difference, but I have never been able to understand it logically.

The wake shape is made with the hull and the water. The only thing you can change is how the boat pushes through the water.

In theory, I could pull the boat at the same attitude with a cable and get the same wake, right?

sethro
08-02-2009, 09:32 PM
Pull in the Course:

The OJ 3 blade had the 'softest' pull of the bunch. Behind the boat the boat felt very foregiving while in the boat there was still very good speed holding ability. The OJ 3 blade in my mind just had a great pull.

Wake:


The OJ 3 blade had a nearly identical wake profile to the Acme. The wake was lower and slightly wider than the OJ 4 blade with no rooster tail at any line length or speed. The OJ 3 blade also provided a substantially softer wake than the Acme. The rooster tail was now completely gone and in its place only soft bubbles.



My findings were just about the same with the OJ XMP 3 blade over my old stock, stainless steel prop...but this was on a 98 Malibu Echelon. I was quite pleased with the improvements of the seemingly softer pull, but more impressed with the improvement of my 22off rooster tail. I went with the 13x12 size as the 13x11.5 increased the 34 and 36 mph rpm too much on my boat.

BrianM
08-02-2009, 10:32 PM
I have never been able to understand how the prop changes the wake characteristics. I know many of us believe the prop somehow makes a difference, but I have never been able to understand it logically.

The wake shape is made with the hull and the water. The only thing you can change is how the boat pushes through the water.

In theory, I could pull the boat at the same attitude with a cable and get the same wake, right?
Props have a lot to do with it. The pitch, diameter, cup and overall surface area of the blades all have an effect on the water creating more or less turbulence and pressure differences in various patterns in the wake. Test a few different props on your boat. There is definitely a difference.

russlars
08-03-2009, 12:09 AM
Props have a lot to do with it. The pitch, diameter, cup and overall surface area of the blades all have an effect on the water creating more or less turbulence and pressure differences in various patterns in the wake. Test a few different props on your boat. There is definitely a difference.
Agreed! Nice write up Brian.:) As you know I went through a similar test on my 205 recently also. I decided to go with the OJ 12.5 X 12 4 blade based on the improvement in the feel of the wake over my ACME 541. I have sacrificed a couple MPH on the top end (which I never use anyway) and the hole shot isn't as good, but I love the feel of the wake with the OJ. Testing is the key to getting just what you want and Eric at OJ is great to deal with. As was stated earlier, the CNC props are great at holding speed. That characteristic alone is reason enough to change if you are still running a cast prop.

Kevin 89MC
04-07-2010, 09:40 AM
Wow, great writeup Brian. Somehow I missed this thread, too busy back then to be on here much. I think I may have to get a few new props to test, interesting how the wake characteristics changed.
Kevin

etduc
04-07-2010, 11:13 AM
Props have a lot to do with it. The pitch, diameter, cup and overall surface area of the blades all have an effect on the water creating more or less turbulence and pressure differences in various patterns in the wake. Test a few different props on your boat. There is definitely a difference.

Also, should be noted. Drive shaft angle, therefore prop angle.

Besides creating thrust, our props create lift. More lift is not necessarily good or bad. The attitude of the hull thru the water (goes back to mfg changing hulls) affects the wake. Prop selection, will affect that attitude, to some extinct.
So we are talking, fine tuning.

Different people, want different things.

Brian's model boat, with a different owner/boat weight balance (gear in boat) people,etc.
Could mean a slightly different prop,or mfg., to achieve the same result.

I use an Acme CNC 541 on my 94, for all around. Wouldn't hesitate trying an OJ.

Good job. Brian.

DooSPX
04-07-2010, 01:37 PM
agreed with everything BrianM has said as well as what etduc said. It all plays a factor.
heck, I can see a difference in my wake on my 91 with as little as 15 lbs give or take.

Ben
06-12-2013, 06:51 AM
So if my goal was to reduce -22 hump, I would be better w the OJ 3 blade than the acme 541? I don't care about top speed or holeshot. Prefer no major increase to rpm, ok with some.

I am running stock 13x13 now.

Ben
06-12-2013, 06:52 AM
Great write up btw. Good time / effort.

I'm sure you hated all the extra skiing and boat driving to check this....

BrianM
06-12-2013, 08:47 AM
So if my goal was to reduce -22 hump, I would be better w the OJ 3 blade than the acme 541? I don't care about top speed or holeshot. Prefer no major increase to rpm, ok with some.

I am running stock 13x13 now.
Yes. The OJ 3 blade made for a better wake on my boat.

BARE5
06-12-2013, 08:48 AM
So with stock prop on a 95 Prostar, which one will keep the top speed and improve pull out of the hole. Even with stock, I can pull 2 barefooters 44mph.

Ben
06-12-2013, 01:10 PM
Thanks. Now I need to see how to get approval after getting an unauthorized Bimini....

Or skip and go to -28.

BrianM
06-12-2013, 04:12 PM
So with stock prop on a 95 Prostar, which one will keep the top speed and improve pull out of the hole. Even with stock, I can pull 2 barefooters 44mph.
You are going to sacrifice a small amount on the top end for hole shot but not much. I posted top speeds of the props above. Its been so long since I ran a Legend 13x13 on my boat I can't remember what it ran WOT with it. Probably right at 45mph. So you loose about 1-1.5 mph off the top for amazing smoothness, awesome hole shot and a better wake. That's a no brainer to me.

BARE5
06-12-2013, 05:21 PM
Thanks. Ordering soon.

perkinsperkins
06-13-2013, 02:37 AM
I just upgraded to the 3 blade OJ XMP 13 x 11.5 from the original 13x13 4 blade on my 1990 PS190. I'm very pleased with the improvement in performance.