Old style Mercury/quicksilver twin bladed prop

[mercuk]

Hi all, there is a marine dealer in the u.k at the moment that is selling off all his old stock of the "old school" Kiekhaefer twin bladed ally props cheap. They are the 15 spline ones.

My question is: My engine is a 1985 75hp 4 cyl Mercury (last of the Kiekhaefer based straight 4's) and I need one that is close to a standard modern day quicksilver 13.25 X 17" 3 blade ally prop.

Anyone know which out of the old twin blade props with a choice of 13 X 17", 13 X 19" or 13.75 X 21" pitch will be closest to a modern day equivilent?!
I'm thinking the 17" one but please bear in mind these are the OLD style twin (2) blade prop NOT 3 blade propellers. Anyone with any thoughts on retro fitting the "old syle" propeller to my engine?!

Many thanks in advance to anyone that takes the time to shed light on this one...

 

[Texasmark]

Re: Old style Mercury/quicksilver twin bladed prop

I had a '59 or '60 25 HP Wizard brand OB which, as the story goes, was manufactured by Merc. Marine to the Merc. Mark 30 spec (looked just like anyway and Wizard didn't make OB engines), with a little detuning and cosmetic modifications. Wizard was the brand name for OB's sold by Western Auto, an auto parts chain that also sold OB engines. It came with a 2 blade alum and I bought a Michigan Wheel 3 blade bronze for it....MW catalog listed the prop under the engine ID column for the Wizard.

Since going from 3 to 4 blade means a decrease of 1" of pitch to account for the "inefficiency" of the extra blade at WOT, one would think that the converse is true and one would add at least 1" of pitch when going from 3 to 2. Published media says that the fewer the # of blades, the less turbulence and better efficiency and for obvious reasons, 2 is as low as you can go.

Merc used the 2 blades up until mid 60's as I recall when they changed their paint color from pastel power heads and off white midsection/lower units, to Phantom Black Lacquer. No reason to change the spline count on the prop shaft so they all should be the same.

HTH,
Mark

 

[steelespike]

Re: Old style Mercury/quicksilver twin bladed prop

Speaking very basically the 2 blade has been thought of as the fastest prop, most efficient design ,less drag.
If brass or stainless should be a little more sophisticated for the time.
I do believe the 2 won't have as good a hole shot as a 3 blade It is logical to increase about an inch in pitch with the 2 blade
though I don't know that as a fact.
The 2 blade may not seem as smooth as a 3, as a 3 may not seem as smooth as a 4.

 

[mercuk]

Re: Old style Mercury/quicksilver twin bladed prop

Hi, Thank you Mark and Steelespike for you valuable input. Although, both posts, from what I can make out contradict each other.....
However, I'm more inclined to go with Texas Marks opinion (no disrespect indended steelespike) and go for a 1" increase if anything..... BUT.....I will never really be 100% until I go out and test both prop's at hole shot and WOT...... (I thinking it might just be that exactly, the 17" for h/s and the 19" for WOT)...
Also looking at my 60's Kiekhaefer's (9.8hp and 6hp both 2 blade) compared to the 72' Mercury (3 blade) it does seem that the 2 blade prop's are definately larger in overall diameter and pitch......

Will let you know how I get on. And thanks again for you input guys.

 

[steelespike]

Re: Old style Mercury/quicksilver twin bladed prop

Yes I knew better, but got confused going the wrong way with pitch somehow associated with reducing pitch when going to a 4 blade from 3. Don't ask me how.
Usually you find a 4 blade to be slightly smaller diameter than a 3 blade thus a 2 blade slightly larger than a 3 blade.
Many times as pitch goes up( unrelated to blade number)diameter goes down.
It will be interesting to see how your props behave.Usually the 4 blade is thought to handle better than the 3.(more responsive) I wonder if the 2 blade isn't as responsive as a 3.

 

[Texasmark]

Re: Old style Mercury/quicksilver twin bladed prop

Many times as pitch goes up( unrelated to blade number)diameter goes down.

I'm not a marine propulsion engineer, but I think that the blades have a fixed surface area and as you bend the blades back, especially when high rake is associated with the pitch change, it just makes the diameter less. But that's just speculation.

Mark

 

[Texasmark]

Re: Old style Mercury/quicksilver twin bladed prop

Speaking very basically the 2 blade has been thought of as the fastest prop, most efficient design ,less drag.
If brass or stainless should be a little more sophisticated for the time.
I do believe the 2 won't have as good a hole shot as a 3 blade It is logical to increase about an inch in pitch with the 2 blade
though I don't know that as a fact.
The 2 blade may not seem as smooth as a 3, as a 3 may not seem as smooth as a 4.

On the 2 blade efficiency, check Chinewalker's Avatar. A little 40's-50's time frame Merc Mark 20 E I think running the Quicksilver racing lower unit with the very small diameter, high pitched, 2 blade bronze racing prop. When I was a kid, that was the setup of choice for local guys running 3 pt hydro's. To get the boats on plane, since there wasn't anything to produce a hole shot, they would squeeze the spring loaded throttle and the engine would throw a rooster tail 30+ feet behind the boat causing some forward boat movement.

After half a dozen squeeze, release events, the boats finally got on the water and away they went.

On no/sloppy hole shot with a 2 blade, that's why Michigan Wheel sold the 3 blades in bronze and finally Merc realized that everyone didn't have a light fast boat that a 2 blade could get up on plane fast enough to suit the owners....took about 1965 for that to happen.

That's what I said earlier about my Wizard 2 blade prop. When I got the 3 blade I called it my "power" prop, used it for water skiing....one 90# soaking wet skier on two skis....running just barely above planing speed....but it was fun..... and the original 2 blade my "speed" prop.....yeah right...speed prop on a 25 hp engine on a heavy 14' wooden boat.....but I was a teenager and just getting started in the boating world on my own.

Yes, the more blades the smoother....BTDT

Course on racing, nowadays they have ocean racers with several, thousand horsepower engines running cleaver props with half a dozen blades. Must work for them.

My 2c,
Mark

 

[Frank Acampora]

Re: Old style Mercury/quicksilver twin bladed prop



Two blade props, especially bronze two blades, have a cachet about them. I like them .

Typical two bladers usually have a slightly larger diameter and a bit more blade area for each blade. Back in the day, they were THE racing blade, but that was before surface running and cleaver props. Today, since racing blades run at the surface, it doesn't matter how many blades they have.

On my little go fast, I lost the 10 1/2 diameter X 14 pitch two blade and am now using a 10 3/8 X 13 pitch three blade. The three blade gives essentially the same performance but just doesn't look as good on the trailer. And, yes, I could feel the rumble of the two blader. In fact, vibration was most likely the reason I lost the 10 inch bronze prop. Tailcone worked or broke off allowing the thrust pin to drop out, and as soom as I slowed down, the prop slipped off the shaft.

Last photo shows a bronze 13 1/2 X 23 pitch Mercury racing prop. It is not the stock thru-hub that old school mercs came equipped with.

 

[Texasmark]

Re: Old style Mercury/quicksilver twin bladed prop

View attachment 176062View attachment 176063View attachment 176064

Two blade props, especially bronze two blades, have a cachet about them. I like them .

Typical two bladers usually have a slightly larger diameter and a bit more blade area for each blade. Back in the day, they were THE racing blade, but that was before surface running and cleaver props. Today, since racing blades run at the surface, it doesn't matter how many blades they have.

On my little go fast, I lost the 10 1/2 diameter X 14 pitch two blade and am now using a 10 3/8 X 13 pitch three blade. The three blade gives essentially the same performance but just doesn't look as good on the trailer. And, yes, I could feel the rumble of the two blader. In fact, vibration was most likely the reason I lost the 10 inch bronze prop. Tailcone worked or broke off allowing the thrust pin to drop out, and as soom as I slowed down, the prop slipped off the shaft.

Last photo shows a bronze 13 1/2 X 23 pitch Mercury racing prop. It is not the stock thru-hub that old school mercs came equipped with.

Hey Frank, while we have your attention, I was attentive to your running a thru hub prop with a red Chrysler tail cone on a non thru prop exhaust engine on your 60+ mph play toy. I don't know the drag dynamics, but if there were any I guess the cone neutralized them.

Mark

 

[Frank Acampora]

Re: Old style Mercury/quicksilver twin bladed prop



Hey, Mark: One thing you first need to know is that Chrysler developed the "flare" washer as a means to reduce ventilation/cavitation.

Initially, when the one piece lower unit was designed, the midsection was (and still is) one inch shorter than the older style two piece. The prop was a one piece with the elegantly shaped tailcone. A spacer ring was also made for use with the more usual closed hub props we see.

Unfortunately, the one inch shorter midleg (while 3 MPH faster) did introduce ventilation with the new props. SO: Chrysler rushed into production the "flare" washer to try to alleviate this ventilation (I am not sure it really does anything, but I do like its look)

Now: back to your question. I have run all these props in various combinations on my 140, less so on the 125 hung on the go-fast. ---Open thru-hub, closed hub, with and without flare washer or tailcone. IN MY APPLICATIONS There is absolutely no discernable difference in performance-other than that directly attribtable to difference between aluminum and stainless. By discernable, I mean that the tach reads the same and speeds are the same within the accuracy of the instruments. Thus, there could be a minor difference that even a GPS would not see. So, as I see it, use of a tailcone and/or flare washer is at the discretion of the owner.

Top photo is a thru-hub exhaust Ballistic with only the tailcone. First two bottom photos are the original stock prop with integral spacer. Third bottom photo is a stock closed hub prop with the separate spacer. Final photo is a Michigan stainless thru-hub with both flare washer and tailcone.

 

[Frank Acampora]

Re: Old style Mercury/quicksilver twin bladed prop



Here is another thru-hub with the flare washer (only) attached.

 

[Texasmark]

Re: Old style Mercury/quicksilver twin bladed prop

View attachment 176077

Hey, Mark: One thing you first need to know is that Chrysler developed the "flare" washer as a means to reduce ventilation/cavitation.

b

I guess I was ahead of a lot of this technology. My Chryslers were a '71 55 on a 16' Chrysler Sport Fury. With a wife and 4 kids, Sunday afternoon fun was somewhat limited, especially when it was my turn to ski. After about 6 months of that I went back to the dealer and paid retail for a new 85, getting wholesale for my (6 mo) old engine that had a couple hundred hours on it, and performance improved significantly. The prop was apparently Chrysler unique, in white alum. and had the tail cone similar to the ones you show. I had no tach and it has been a long time so I can't provide any specs on performance other than the 85 made a good power plant for the boat and load. Had no mechanical problems with either, course they were new and the next season, I went with a bigger boat from a different dealer who sold Johnsons and Caravelles.

Thanks for the reply,
Mark

 

[mercuk]

Re: Old style Mercury/quicksilver twin bladed prop

So before my thread got hijacked, the upshot of it all was that I'm better off going for the 13x19 two blade prop for my Merc 85' 75hp. But its not going to be a smooth as a modern three blade prop, and may vibrate some what....
It did have a 3 blade quicksilver 13.25" x 17" prop before I dinged it up. It now has a piranha 13.75" x 15B prop but it can rev far too hard(6k+) at WOT unless I trim it back.

Its either the two blade 13 x 19 or move up a size on the piranha prop. I'm probably going to go for the two blade as its the cheaper option and at ?25 including delivery (seems in good condition too), I can always use if for a spare if I don't like it I suppose....

 

[Frank Acampora]

Re: Old style Mercury/quicksilver twin bladed prop

Sorry about that hijack, but yes, you would be better off with the three blade. Of course, money is always a factor and that, in your case, seems to dictate the old style two blade.

And as you said: The price is cheap enough that you can always use it as a spare.

You may or may not feel the extra vibration. To clarify an earlier reply: I did feel it on my 15 footer with a 55 but when I mounted the engine on a 10 foot tunnel hull, I no longer felt it (probably because the hull was dancing around so much). It was still there though since it did cause the tailcone to come off and I lost the prop.

 

[Texasmark]

Re: Old style Mercury/quicksilver twin bladed prop

So before my thread got hijacked,

I did it and I apologize. Frank does a lot of experimenting with the Chrysler/Force engines and he joined the conversation and I hit him with my question while we had his attention. Props and performance of such are part of his "research" so it was in the "gray zone" for hijacking and I took advantage of the opportunity.

Mark

 

[mercuk]

Re: Old style Mercury/quicksilver twin bladed prop

I did it and I apologize. Frank does a lot of experimenting with the Chrysler/Force engines and he joined the conversation and I hit him with my question while we had his attention. Props and performance of such are part of his "research" so it was in the "gray zone" for hijacking and I took advantage of the opportunity.

Mark

Not to worry...
It was really interesting to read, but I don't have any Chrysler engines so was all a bit alien for me

One last Q if you don't mind though please.... I did buy a 13.25 x 17 stainless steel prop for it but I was so shocked at the weight of it compared to an normal aluminium or piranaha prop I sold it on with out even trying it. I mean is it normal for stainless props to be sooooo heavy?!!
This thing must of weighed like 20lbs+...
I just though it would strain the engine rather than improve the performance just because of the sheer weight of the thing.....

 

[Texasmark]

Re: Old style Mercury/quicksilver twin bladed prop

Not to worry...
It was really interesting to read, but I don't have any Chrysler engines so was all a bit alien for me

One last Q if you don't mind though please.... I did buy a 13.25 x 17 stainless steel prop for it but I was so shocked at the weight of it compared to an normal aluminium or piranaha prop I sold it on with out even trying it. I mean is it normal for stainless props to be sooooo heavy?!!
This thing must of weighed like 20lbs+...
I just though it would strain the engine rather than improve the performance just because of the sheer weight of the thing.....

Don't sweat the dead weight of the SS prop. When compared to the thrust that the prop produces it is miniscule. Not my words but words from more knowledgeable folks on here than my humble self. I have run SS since 1973, and will not run anything else..........in clear water where no under water boulders are present. Course folks on here state that they can tear up LUs with alum as well as SS if you hit a really big one at the right rpms.

However, with that said, I can notice a high pitched SS prop on my 3 cyl engine at idle and a lower pitched SS of lighter weight doesn't produce the noise...but I attribute that to pitch and weight, not weight alone.

Go have fun.

Mark

 

[Frank Acampora]

Re: Old style Mercury/quicksilver twin bladed prop

Well, There is a thing called inertia--you know: A body at rest tends to stay at rest. The heavier stainless prop will take more horsepower to spin it up to speed BUT----the difference is so small that you will never notice it AND--it will most likely be offset by the increased efficiency of the stainless anyway.

In fact, a number of years back when dragsters were still shifting, it was all the rage to use a heavy flywheel for the extra inertial "lurch" at shift. It tended to keep the engine RPM up when it was shifted to a higher gear

The big argument that people here on the forum have against stainless is that you will destroy your lower unit if you hit rocks (or anything). Me? I don't go out looking for rocks to grind up with my prop and I generally follow the charts and channel markers. The once or twice I did decide to cut up some big stones, the rubber hup protected the lower unit and the blades bent nicely to the tune of money. In fact, the hit did not seem too bad and I ran for another hour. When I got to a beach and checked, all three blades were bent and the skeg was gone.

There is no question that newer designed aluminum props can approach the performance of stainless so really, it becomes a matter of personal choice. But also remember: When it comes to the slight edge needed, all the racers use stainless props

 

[mercuk]

Re: Old style Mercury/quicksilver twin bladed prop

Frank and Mark you guys have really helped me out on this thread and taught me a few things along the way as well. For that Sirs, I am very greatfull.
By the way Frank, I can totally relate to what you said about the flywheel on the dragsters. Makes sense.
Anyway, just to keep you updated, I decided to go for the two bladed "old school" one and when it turned up today I was a bit cheesed off.
It WAS a mint propeller when they sent it out, however the dumb $ss who works for the company couldn't be bother to package it properly and it got bent up and chipped in transport.
So I'm going to sent it back and they said they can offer a replacement or get my money back..
Ive seen a second hand POWERTECH ss prop for a fair price in 13.25" x 17" size. I think it has m135red3r-17 stamped on it. I'm wondering if anyone has any experience with these propellers and if there any good?!
All the best, Marc.