211 Liberator prop question

[onebadbowtie86]

Hey everyone, Springs around the corner and I need to get my prop issues worked out. I have an '89 211 liberator with the 5.7 omc cobra. I bought the boat with a blown outdrive last June, replaced the drive with a good used one, that is the correct gear ratio. We used the boat almost every weekend and it has been great. The boat came with a SS prop, that I couldnt find any serial numbers or name on it but it says its a 14.5"x 20"p. The prop worked ok, I was able to get a best of 53 mph gps out of the boat, but I was running 5,000 rpms. Towards fall I bought a brand new omc ballistic 21" thinking it would get my rpm's down to where the should be and it brought them down to 4,000-4,200 with just myself in the boat, with a top speed of 49 mph gps.

What Prop came with this boat, or is known to work best? Obviously the ballistic is too much prop. Would it be cost effective to have a prop shop tweak this brand new prop, or see if someone wants to trade for a 19" or 20"T?

 

[jestor68]

Re: 211 Liberator prop question

Something is not right here. You don't get a 800 rpm change with one inch of pitch.

It sounds like that original prop is more like a 17 pitch that somebody re-pitched; even though I'm not aware of being able to re-pitch one that much.

Given that you were turning 5000 rpm with a prop of unknown pitch; and now you are turning 4200 rpm with a prop of KNOWN pitch, I would work from the Ballistic's results and drop to a 18 pitch to get the rpm where it should be.

 

[onebadbowtie86]

Re: 211 Liberator prop question

Ya Thats why I was a little disappointed When I put the new prop on. I am pretty much disregarding the original unknown prop. I think I read some where that these boats originally came with a 19" SS prop, but would like a confirmation if any one knows? Maybe a 19" viper prop?

 

[dan02gt]

Re: 211 Liberator prop question

You could have a prop shop take a 1" of pitch off of it and that would help bring your RPMs up 150RPMs or so. The big thing is getting the right prop for your boat. Your boat is heavy and is going to need a prop that has the diameter, rake, and cup to get that bow in the air and reduce your wetted surface area to make it go fast. A Mercury Tempest Plus, Rev4, or Bravo 1 would probably work good on your boat. How much h.p. does your engine make and what is the drive ratio?

 

[onebadbowtie86]

Re: 211 Liberator prop question

I asked the prop shop by my house, and it just wouldnt be worth the money to have a new prop repitched, I could just buy a different prop and sell this one. I really like how much bow lift the ballistic gave the boat, I wish I could get the ballistic, or atleast its performance in a 19"

My boat has the 270 hp 5.7 with the 1.41:1 out drive. The engine is strong and in good working condition considering I can still get good mph out of the big boat, just trying to get the best performance out of the boat.

 

[dan02gt]

Re: 211 Liberator prop question

OK those are the numbers we need. With the 20P prop that came with your boat you are showing a awful 24.3% slip. In other words your 20P prop in a perfect world would be moving your boat forward 20" for every revolution, but you are only getting 15.2" per revolution. In the real world your boat properly setup should get around 14% slip. Your original prop probably has all the cup worn off of it so your able to spin it like a 6" wide tire on a 600HP Corvette. You stuck a good 21P prop on it and it's just too much and you don't have the power to turn it. My best suggestion would be to change out your 21P Ballistic for a 19P Ballistic or one of the others I mentioned. You are showing less slip with it (the Ballistic) at around 18% and the 19P should get your motor back up into it's power band giving you the speed you lost back and maybe a little more.

 

[onebadbowtie86]

Re: 211 Liberator prop question

I dont know much about props, and the cupping being out of my origina lprop makes sense, the edges are a little knicked up. Is there a 19" ballistic prop?

 

[onebadbowtie86]

Re: 211 Liberator prop question

I dont know much about props, and the cupping being out of my origina lprop makes sense, the edges are a little knicked up. Is there a 19" ballistic prop?

 

[NHGuy]

Re: 211 Liberator prop question

Nice boat!
Yes, Ballistics are available in 1" increments. Many Liberator owners on another forum I frequent like them. Their shape is kind of interesting, they have a bit of extra blade at the outer edge.
Have you tried trimming for speed? Sounds as if you understand it...on plane you raise the drive to lift the bow. Be careful though, if you get the trim too high the prop will slip or sometimes the boat will porpoise. That's what happens when the bow rises and falls in a cycle. Either thing is corrected by lowering your drive a bit. Just don't let the motor rev too high, that can break stuff.
Ballistics have a big blade so they bite well. If your old prop is a nicked up aluminum 3 blade the Ballistic 19" 3 blade would be good. If you are going for a 4 blade you probably need a 19" or less. The 4 blades bite better because they have more contact area.
I'd ask the prop shop guy if he thinks he can fix your old prop for a backup or for when you have a full load in the boat. While talking to him tell him what is happening with your boat. I'm sure he wants your business. It ain't as cheap as mailorder, but it's a service, and I bet by inspecting it he can tell you a lot.
Good luck.
And welcome to the forum!

 

[onebadbowtie86]

Re: 211 Liberator prop question

Thanks for the help guys! Yes I understand trimming the boat out, with the ballistic I didnt need to trim the boat out as much, I really liked everything about the ballistic except for too low of rpm. I will ask about getting my old ss prop fixed up for a spare, and look for a 19" ballistic. Anyone looking for a 21" ballistic with 45 minutes of run time?

 

[NHGuy]

Re: 211 Liberator prop question

If you haven't trimmed up at least see if it will make 4400 rpms unloaded and trimmed out on some early morning flat water day!
That's when I go get my top speeds.

 

[onebadbowtie86]

Re: 211 Liberator prop question

I did have the boat trimmed out as far as I could with both props. With the omc, I dont have a separate trim button, just the up/down. It was a calm day when I was testing and the highest rpm I could get was the 4,200 trimmed out. I really would like to get this thing running 4,600 rpm's so I guess the 19" is the way to go!

 

[dan02gt]

Re: 211 Liberator prop question

I think the 19 is definitely the way to go and it seems your boat likes the Ballistic. Not needing to trim as much means your getting better bow lift and that is a good thing. Could you send the 21 back and get a 19?

A call to a prop shop might be a good idea too. I would recommend Mark at Mark's High Performance Propeller: Mark's High Performance Propeller. He does good work and will take the time to answer your questions with honest answers. He may be able to get the performance out of your 21.

 

[onebadbowtie86]

Re: 211 Liberator prop question

Thanks for the link, I will call him.

Unfortunately I cant return the prop, I bought off a forum from a member that never used it. Hopefully I can sell it and get some of my money back. I'll probably end up getting the ballistic 19" unless someone else chimes in with a better suited prop.

 

[Tail_Gunner]

Re: 211 Liberator prop question

Something is not right here. You don't get a 800 rpm change with one inch of pitch.

It sounds like that original prop is more like a 17 pitch that somebody re-pitched; even though I'm not aware of being able to re-pitch one that much.

Given that you were turning 5000 rpm with a prop of unknown pitch; and now you are turning 4200 rpm with a prop of KNOWN pitch, I would work from the Ballistic's results and drop to a 18 pitch to get the rpm where it should be.

Hey everyone, Springs around the corner and I need to get my prop issues worked out. I have an '89 211 liberator with the 5.7 omc cobra. I bought the boat with a blown outdrive last June, replaced the drive with a good used one, that is the correct gear ratio. We used the boat almost every weekend and it has been great. The boat came with a SS prop, that I couldnt find any serial numbers or name on it but it says its a 14.5"x 20"p. The prop worked ok, I was able to get a best of 53 mph gps out of the boat, but I was running 5,000 rpms. Towards fall I bought a brand new omc ballistic 21" thinking it would get my rpm's down to where the should be and it brought them down to 4,000-4,200 with just myself in the boat, with a top speed of 49 mph gps.

What Prop came with this boat, or is known to work best? Obviously the ballistic is too much prop. Would it be cost effective to have a prop shop tweak this brand new prop, or see if someone wants to trade for a 19" or 20"T?


Towards fall I bought a brand new omc ballistic 21" thinking it would get my rpm's down to where the should be and it brought them down to 4,000-4,200 with just myself in the boat, with a top speed of 49 mph gps.

The last sentence makes sense that that boat will not turn a 20 if it has 1.5 gearing.

21p @ 4200 with 1.5 gearing 49 mph gets 13% slip....very reasonable number for a ballistic
21 p @ 4800 1.5 nets 56mph @ 13% slip

19p @ 4800 1.5 10% slip nets 52mph.

Check your tach for accuracy.....boat tach's are very well known for miscalibration. You may want to try a Stiletto or Solas for that boat a better match to that hull

 

[HT32BSX115]

Re: 211 Liberator prop question

Towards fall I bought a brand new omc ballistic 21" thinking it would get my rpm's down to where the should be and it brought them down to 4,000-4,200 with just myself in the boat, with a top speed of 49 mph gps.

The last sentence makes sense that that boat will not turn a 20 if it has 1.5 gearing.

21p @ 4200 with 1.5 gearing 49 mph gets 13% slip....very reasonable number for a ballistic
21 p @ 4800 1.5 nets 56mph @ 13% slip

19p @ 4800 1.5 10% slip nets 52mph.

Check your tach for accuracy.....boat tach's are very well known for miscalibration. You may want to try a Stiletto or Solas for that boat a better match to that hull

Yeah. That's the FIRST thing I would check.


The boat in my "SIG" had an OMG 460 King Kobra installed when I got it. It had a 19p 3-blade SS (re-pitched/cupped to 20) prop on it. It would turn about 5000 RPM and go 60 MPH with that prop.

My spare prop was a 17 pitch SS prop that I never used. (it was a spare!) My brother tried it and it came out of the hole a little better but at 5000 RPM would only go a little shy of 50. (that's why it was a spare!!)
I have since removed everything OMC and replaced it (......still have the props though .........)

Your 350 CU-IN SBC will NOT turn the "right" drive on a 211 Lib with a 20P prop at 5000 RPM. (period)

Check your tach against a KNOWN tach, and try a 17p prop. (if you lived close to me you could try either of mine!)
You MAY be able to try a 19p prop.

If I'm not mistaken, you have a 1.41:1 drive. (mine was a 1.43:1..)

Either way, a 21p prop is TOO MUCH for a stock 350 in a 211 Liberator.

You want either a 19p or 17p prop.

I don't have a service manual open in front of me but I think your 350 wants to turn around 4600-4800 RPM at WOT.

Prop your drive so it turns at MAX RPM (4600-4800) when you're lightly loaded.

If you don't prop for the highest RPM, your anemic hole-shot will be REALLY anemic!

Mine was, even with the 460! (until I replaced it with the 454/Bravo III)


Regards,


Rick

Let me also add that if you CAN turn 5000 (engine) RPM with a 20p prop on that boat (meaning your tach IS correct) Then you do not have the "right" drive on the back. (I.E. it's NOT a 1.43:1 drive)

 

[onebadbowtie86]

Re: 211 Liberator prop question

Thanks for the insight guys. The boat does have the correct gear ratio drive meant for the 350. The 20p prop that came on the boat probably has been beat up and fixed before or something. It definetly doesnt act like a 20, more like a 17. My tach is also within 100 rpms, or close to that when I checked it last summer. Based off my findings with the new 21p ballistic I plan on getting a 19" ballistic. How is the solas or stiletto better suited then the ballistic?

 

[Tail_Gunner]

Re: 211 Liberator prop question

If you go to the top of the forum and check walleyehed's prop testing at the bottom of the page he points out the ballastic is not a heavy load prop and you do have a heavy boat.Stilletto's are known for aggressive cupping and high lift. The higher the lift the less wetted surface and higher speed's. Solas has a very good design at the same time and if i remeber correctly it is availble in a 18p 3blade.

Either of those two prop's should drop your slip into the 9/10% range.

 

[HT32BSX115]

Re: 211 Liberator prop question

Either of those two prop's should drop your slip into the 9/10% range.

Best slip I ever got (at WOT) with my King Kobra powered Liberator and a 20P (stock OMC) prop was about 9%
(1.43:1 drive, 20p 3 blade, 5000 RPM, 60 mph) Speed was measured with radar, but the tach was not verified with another tach.

Now, I get 10% slip with the Bravo III (4600rpm [new tach], 1.81:1 drive ratio, 26p prop(s), 57 gps mph)

I would have expected the slip to be substantially less at approx the same speed with a Bravo III.

Makes me think the tach is suspect in either (or both) case(s).

If you don't have a known (verified) tach and accurate speed measurement, the results are basically meaningless.

 

[onebadbowtie86]

Re: 211 Liberator prop question

So would a viper, stilletto or solas all be better props for a heavy boat then the ballistic?