When to "Re-condition" Props

Jack380AC

Jack380AC

Member
Jan 28, 2008
878
West Chester, PA / North East, MD
Boat Info
2000 380 Aft Cabin
Engines
Twin 454 Mag MPI Horizon MerCruiser
The real answer is: it could be any of a 100 things. I know that. Just which ones and in what order do I plan on checking/fixing them?

Background: Boat just does not have the zip it used to have. Not reaching cruising speed. Feels heavy in the water. Botom paint does not appear to be built up.

One friend on the dock has suggested that it is a good investment to have the props pulled over the winter and reconditioned. Eliminating that as a potential problem would be a good start says he.

That suggestion also begs the question of how to economically determine if I have the optimal props for my boat as currently outfitted/used.

Thanks in advance for any suggestions.
 
After about 200 hours the bronze will have flexed enough to no longer be at peak performance. Having props re- conditioned only bends them back to where they use to be. They will quickly reset back to where they were. conditioning is great for balance and vibration but will not give you the efficiency of a new set made out of quality metal. I replaced my props with a new set 2 years ago same pitch. I would typically cruise 19.5 . The new wheels got me to 21 at the same rpm. What this means is the new wheels were not slipping as much.
Now I am sure you could put alot more the 200 hours on a set of wheels. most boaters never change them unless the hit something. but ask anyone who put on a new set. they will probably tell you there was a substantial improvement.
This may not be the answer to your problem but bending metal is only going to be a short term solution
 
Jack,

The question is, did you ever do a prop scan on this boat?

I've done my props last year and here's the quick summary of the process:

1. The first step is prop scan and data analyses. The props are not reconditioned if they don't have to be.
2. The tech will advise as to what category type your props should be (to deliver best performance for your boat) and will make the props fit that category.
3. If one or both of your props will match the required category, then all you need is a prop tuning (may be that's what you meant by reconditioning).

My props had to meet category 1. The prop scan data showed that one prop was matching the specs and the other was not. So the approach was to do a basic tuning for cat1 prop and recondition the other prop to meet the specs for cat1. If my memory serves me right, I paid $300 total ($200 to recondition one prop and $100 to tune the other prop). Before proceeding with this my boat performed well and met the specs. But, I did the prop scanning because one prop had very tiny bent and just to re-assure that my props are matching the specs. After the tuning my performance almost stayed the same. I saw very tiny improvement, but realistically I didn't expect any, b/c as I had mentioned the boat performed to the specs to begin with. I picked up 1mph and gained 20rpm on one side and about 40rpm on another side. I can't credit prop work for the improvement, b/c such a slight change can be due to slight differences in wind, seas, fuel levels, etc.

So, going back to my original question, if your prop have never been scanned, it’s no brainer that it’s time to do it. If they have been scanned few years ago, I would still scan them and expect performance improvement providing the engines are performing fine.

I've used these guys: http://www.atlantispropeller.com/ and would highly recommend them. Since you're in PA it might not be too far from you.


Hope this helps.
 
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FireIsland1 said:
After about 200 hours the bronze will have flexed enough to no longer be at peak performance. Having props re- conditioned only bends them back to where they use to be. They will quickly reset back to where they were.
Click to expand...
I have never heard of this. When you say "quickly reset back" what are you basing your statement on? If this is true I would sure like to confirm.

I have never heard any prop expert mention this after confirming bronze prop material.

With so many threads on this sight and others recomending adjusting pitch/cup I would have thought this would have been mentioned before.

Someone please confirm.
 
I'm with HIFI on this one.........

FireIsland - can you give us some authority for props flexing, taking on a new shape then resetting themselves after re-pitching?


If that is true I need to send a memo to my props........they were re-pitched after the bottom jumped up hand hit them in 1998.........then I had a run-in with a crew boat wake in a narrow channel in 2007 and had both props checked and trued. The damaged prop had 2 blades bent, but the pitch on the undamaged one was within .01" on each blade of the way the prop shop left it 9 years and 950 hours before.
 
I was wondering as well. Maybe it doesn't apply to Nibral?
 
Please don’t admonish me for being stupid, but I was told by my lead mechanic that the props can only be reconditioned twice. After that you need to buy new. Is there any truth to this?? I ask because it was my intention to have both sent out before my spring launch.
 
There is one of those guys in our marina that just ought not own a boat. He is one of those fellows who is so brilliant that he can't learn and doesn't need to listen. He's owned his boat.....a 340DA..... since 2004 and crosses on the back side of the same bouy about every other month. The mechanics call him "Capt Crunch" he's hit that oyster bar so many times. I know he has had his props straightened at least 20 times, so based on that experience alone I can't accept the "recondition twice" thing, unless you want to sell props.
 
Ok I see we have a start of a good discussion. I am fully aware that many boat owners are on their first and only set of wheels. So you put hundreds of hours on the engines , you don’t hit anything and you don’t feel any vibration. The boat runs fine. Then I come along and say your props are done after just 200 hours, what gives?
I never said you have to change out the props every 200 hours and that figure alone will be affected by many factors {quality of material, hp, load, torque, stress }.
I did say they will not be at peak performance and I stand by that statement . I will try to explain what is happening.
Regardless of 3 or 4 blade, as the wheel turns the load on each blade is different. Depending on the hull configuration, tunnel shape, shaft angle, strut shape all effect blade load. The load on the blade at the top is different then the load at the bottom. Water just doesn’t flow perfectly under a hull. So as the blades change position during the rotation they are loaded and unloaded. Your props are not just turning, they are being bent back and forth during each rotation. Some metals can handle this better then others.
Outboards and outdrives often dump the aluminum and go to stainless. This stops a lot of the bending and really gets the boat out of the hole. Bronzes come in may qualities, some great some not so great. Unfortunately price is a big factor. Which means the props you got with your new boat might be at the lower end.
Now you didn’t hit anything and you have no vibration. So why would you even consider reworking the props. It’s simple. The boat just seems to have lost something. A little of it’s get up and go has gone up and went. Just as engines lose hp, bottoms get a little heavy from too much paint, your props are also getting tired. They have pushed 20,000- 30,000 -40,000 lbs of boat , powered by hundreds of hp through seas that are trying to stop you in your tracks. And remember each single blade is taking the load
at different pressures on each rotation.
So you decide to rework the props to get back a little performance. A good shop will be able the reset the pitch that was lost, balance the wheels and polish the blades. And with today’s technology, do it quite well. But what really happened. They bent back the blades right where they were bent from all that load. I’ll give you one guess where they are going to bend next time you load them. Then the edge is trimmed or ground to reshape the diameter. Then the surfaces are ground and polished. Now a good shop is going to have very expensive equipment to measure and balance your props, they will do a great job and keep you from spending thousands of dollars. But the metal you came in with is the metal you leave with. Oh don’t forget you left some metal behind on the shop floor. When Hack4 says he thinks you can only do this 2 time, he’s probable right. How much ‘’extra “ material do you think a prop has.
I have had reconditioned wheels on many of my boats. They will get you back out on the water without killing your pocket. I am not saying don’t have it done or that it’s a bad thing. I’ll bet must used boats out there are on reworked wheels and no one is the wiser. But I stand by my statement. You can’t beat quality new wheels.
I hope that I explained myself and didn’t offend anyone. Just check with other members that have installed new wheels and ask them if they had major improvement in performance. I think they will back me up.

 
FireIsland1: I am by no means a prop tech... In a quest for knowledge I did do some extensive research on props some time back.

Prop flex: I think what your referring to is when a prop shop thins the blades to get performance from a given prop.
Thinning the blades lightens the prop, reduces drag and greatly improves performance. Unfortunately this limits the amount of horse power the prop can hold. Merc offers some pretty good info just in there selection guide. I believe alum is only recommended up to 300 horse or so.

Also your post on how the prop is loaded unevenly per blade due to water flow from the hull was a little confusing for me. I would think this would set up some kind of vibration of sort...but that’s just me not understanding fully.

OP: I think its time to re-con a prop when you think you have a problem with them. Little imperfections that may cost +/-50 rpms and 1mph or so I don’t think is justified.(a fellow boater told me I could spend the whole summer screwing around with props, so I didn't). Obvious damage would be the red flag... If you can look at them, rotate them by hand and visually check the runout, that may be a start. ...Ron
 
So, my example, 9 years and 950 hours on props that have been reconditioned 2X and they are still within .01" or .045% of the way they began. How can that be if your discussion is correct?
 
fwebster said:
So, my example, 9 years and 950 hours on props that have been reconditioned 2X and they are still within .01" or .045% of the way they began. How can that be if your discussion is correct?
Click to expand...
Frank: not sure who your response was directed to. Thought I would just clarify my response on thin blades!

From what I read on prop shop services and pricing. High performance tuning is when blades are thinned and all that. Common sense tells me your not going to have your blades thinned too many times before scraping the prop. I also believe you don't have to thin the blades whenever you recondition a prop. So reconing, repairing can be done many times as long as the tech doesn’t start thinning the blades.... For some reason I think you already knew all this? ...Ron
 
I'm certainly not an expert on props but have had some reconditioned with good results. In 2004 I had my then new nibrals prop scanned when the boat had about 35 hours on it and to my surprise there was quite a lot of room for improvement. Essentially I picked up 2 MPH which doesn't sound like much, but I was impressed that a 19,000 pound boat with a hardtop would do 41 MPH after the scanning and adjustments. I recorded my rpms and speeds and have kept this information. Each year I see if the boat will still achieve the same speeds. I also check my fuel use and look for changes. So far those 2004 props are still doing the job. I also had my new spares scanned and adjusted, but have never had the need to install them. Some day I may change them out to see what the results are. They have just 35 hours on them. Should the boat develop a vibration or change in performance, props would be on my short list of things to look at, but so far I've not had a reason to do anything with the current set up. Prop scanning and performance data gives you a basis for evaluating not only props, but also the general state of affairs concerning your boat.
 
I never heard that the props return to the pre- conditioned level. However speak with Mark at Long Island Propeller in Middle Island on Long Island NY. This guy knows everything about props.

Long Island Propellers is located at 1509 Rocky Point Rd Middle Island, NY.
Phone: 631-345-6295.

2004 320 DA T 350 Mags
"Summer Wind"
 
Hmm - from my engineering school days, i had taken a materials engineering class. I seem to remember that each time you work a metal (similar to a bending motion) the material will become less malable and more brittle. With that in mind, after a prop is straightened, conditioned, put back into place, wouldnt the prop resist flex? Just some information for thought in this discussion. Sort of like removing the tab on a can of soda, same scenario. You work it until brittle and then it breaks off.
 
I do mine every season, not much is more important then balanced props. I also use "atlantis propeller" Ray's the owner an prop scan diales them in.
 
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