Acme 540 prop question

I think you have opened up a can of worms....
1/2 in. is too close , prop burn at that point will result.Also I could not get the performance out of any Acme, Austrel, Federal nor OJ in the 13 in size.
After a year of different props makes, 3&4 blades, 13,14,15 pitch I found the dream prop........OJ Legend 12x15........Boat dr

This is the whole reason why I bought this prop for this boat in the first place is because of Keith's comparison with his 79 mustang.There the same boat same hull design ,just a year off from one another.Plus on top of that its the prop that Delta propeller suggests on using.Boat dr, your going to have to explain to me what prop burn is.I have never heard of that before.I just had a funny feeling when I put it on,it just looks so big underneath the boat.

Since I'm not as familiar with the Acmes as I am the OJ's, can someone tell me/us what the next larger pitch size is, up from a 540. My reason for asking is simple in that as you may recall, I had Acme cut down a brand new 540 to a 12" dia to give it a try after experiencing EXACTLY what Pete's post "the Tique and the 540" revealed. However, cutting the dia 1" resulted in too many rpms and the prop is now destined for another boat with a lower power to wgt ratio. So back to the original question, a higher pitch prop would work better with an inch dia cut from it and more closely and correctly replace a 12x14. Otherwise, I don't see Acme making a new one from scratch, but if there's enough interest........

Peter,is that what you are running on your Tique right now is 12" OJ?What is it a 12x_ prop.I'm kinda interested in what Keith had with his boat,if he had the same clearance issue.

Brian, The 12X14 OJ is on the Tique. In my original thread reporting the results on the 540, I think I mentioned I ended up with 5/8" clearance. This is well below the 10% of prop dia. that the prop guys want. I'm sure it is a issue with Keiths boat too. A 12" prop would use the same strut even on a different hull.

Reid, I'll have to look and see if Acme makes a steeper prop. Off hand I don't think so.

Prop burn is caused by cavitation of tiny air bubbles getting caught in the turbulance of the prop. The prop being so close to the hull, it creates this turbulance. Normally with the proper distance, any air in the prop wash just gets blown out aft. The picture really shows the begining stages where the surface of the gel is etched, pitted and chunks are falling out. In later stages, the even softer poly resin under the gel will start to burn off. This burn is just like a centrifugal pump with a poor inlet design or too small of a inlet. The pump starves for water and traps the air bubbles. In time they will burn through a cast iron casing and destroy the volute on the impeller.

bmiller wrote: Peter is that a OJ legend prop.I notice there are two different OJ brands on Delta's site.So what kind of performance are you getting with your 12x14 OJ compared to the OEM prop that you had on there before?I'm also assuming that its also a 3 blade prop.

Brian, It is the OJ Legend 3 blade. It came with the boat so the only thing I had to compare it with is the 540. I could go to a 12X13 and probably gain some hole shot and a couple hundred RPM's at the top end (about 4300 now) but decided to leave it as is. With the kids driving it, I didn't want to worry about over revs. With me driving it I would know to keep a eye on it. Of coarse I'm the one who went out in it and did a power turn (something I hadn't done since the 70's in my Cuda) and ended up snapping some ribs!!! The kids did find out about that and I did take some abuse for it - the wife told them!

It's hard to say how long it takes for the prop burn to do major damage. The etching of the gel will start right away. If I had to make a guess at it, I'd say 20 hours. Try the 540 and you will know within 20 minutes if it's the prop!!

Well I am looking for a better hole shot to begin with.Also I mosting ski with my boat more than anything else.Thats the reasoning with going with the 540.It won't be till the weekend till I can get it out anyway to test it.Peter,when I do finally try the boat out what should I be looking for in terms how everything should feel.I know its a question that does have a "gray" area to it.I'm just trying to get a idea.I think I'm also going to call Delta and see what they say about the clearance issue.TRBenj I hear what your saying,hopefully I'll be one of the one's that this works out ok for.My gut tells me something different.If thats the case I'll be on the site selling a prop that I can't use.

Brian, I just found this in the Q&A section on Delta's site:

Q. How close to the bottom of the boat can the blade tips run and what is the required aperture clearance?
A. The clearance between the propeller tips and the hull should be at least 1/6 to 1/7 the propeller diameter. Clearance is equally important along the forward edges of the blade where they swing in line with the deadwood and should not be less than 1/12 of the diameter.

Depending on where you measure, it figures out to 1" to 2"

My biggest concern was not the cavitation in the turns (it wasn't worse in the turns) but the amount of hull harmonics it produced. The hull literally buzzed at all speeds. I immediately knew there was a cavitation problem but not caused by turning. I've seen enough prop burn to know what was going on. If you do have the same results, I would stick with the 3 blade Legend based on my but especially Reids experimenting.

Edit: Sorry Doc, your experimenting too.

Boat dr I understand what your saying.I don't want to get the answer that I want to hear.I just want the right answer period.Thats the reason I'm on here asking people.

Tim, I had used General Prop for several years before I bought my Skier.
I had very little knowledge of the props used and the behavior of a 1 to 1 ratio.The leaning curve was steep, but Larry and Joel shared their expertise and their inventory with me.
Did not keep a total # of props I was sent as a test bed on this old CC . But the story goes like this as to the 13 in dia. props.
They were all brand new ,3 blades or 4 blades, cupped or uncupped, box stock or highly modified.
Acme, Ausrel, Federal. Michigan in all flavors. They all worked they all were better than a bent up stocker,But......
The OJ 3 blade legend in a 12 dia. was the magic bullet, still tweaking but for now I an running a 12x15 and sill turning a little too many R's.Eric is gonna rework my 14 to a 15 and and some cup to see just for giggles......
   

If you put a 13" diameter prop on any hull designed for a 12" you're gonna have problems, no matter which MFG. An ACME 540 is debatably the best choice for a direct replacement prop for the Federal 13x13 on a ~18' Ski Nautique.

The Acme 540 gets mixed reviews, I have one and love and hate it. For skiing and pulling it performs great, not for top end performance and certainly not for an afternoon cruise. It revs higher than the 13x13 oj that came off therefore pulls better but drinks a lot of fuel. There is also a harmonic noise with mine that will have you ready to jump out of the boat after a few minutes of cruising.

I truly feel the Acme props are "purpose built" and one single prop will not get you the perfect set up for all situations.

I have 3 props for my boat depending on what I'm doing. Obviously the 540 goes on when we're boarding or skiing all day. I put on my 13x14 OJ when I know all I'm doing is cruising the river, I can cruise at 36mph and still be under 3k and before my secondaries are kicking in. The old OJ 13x13 is still a great prop for everyday use, it skis OK and cruises OK.


Reid, Acme makes a 13x14, I don't know what the model # is but a call to Bill Weeks would get you what you need. I don't think a stock 351 could turn it. I still wish they would build a 13x13, I think that would really benefit someone with a little more motor than stock.

Also, my 540 runs smoother than either of my freshly reconditioned cast OJ's. I'd like to try some other wheels but that's a pricey game.

Acme makes a 13x13 in LH 1 1/8". They don't make one for RH?

The only down side I saw to switching to the Acmes is that idle speed increased enormously.

If you're replacing a 13x13 Legend, I bet you'll love it.

Yes Reid I am very interested if you could send me that prop.I appreciate the offer to use the cut down 540.My # is (859)283-9364 Or I can give you a call.What ever you want to do.