# SS PROP VS ALUMINUM



## scoobeb (Jun 21, 2016)

I'm debating on getting a ss prop over the aluminum prop I have now. The motor is a 20hp 2stroke mercury that has the standard 13 pitch prop on it now. The motor has great overall top end but I wanted to know if I switched to a 13 pitch ss prop will it get me out of the hole faster due to it's limited flex over the aluminum prop? I just want that little bit of extra torque I have been told the ss prop will give me but I want to hear from you guys and real world experience with them,switching them out. I want to know if I should stay at a 13 pitch or go bigger or smaller? I know this motor could spin a 14 without issue but will it benefit me any or just stay with a 13 or possibly go down to a 12. If anyone can chime in on this I would be much appreciated. As of now I get a unbelievable wot of 30+ mph with just me in the boat and near 29mph with 2 people plus all gear out of an aluminum prop and the torque could be a bit better out of the hole,that is my main concentration, to get better out of the hole torque while keeping or even gaining wot speed I'm getting now. If it's not going to benefit me any then I will buy the same prop just a new one and using the one on it now as a spare.

Any advantage on the quicksilver prop over a Solas prop? Any particular aluminum prop better for my 20hp,if I go ss I'm going with Solas since they make great props as far as I know,unless someone can lead me in a different direction for the best overall ss or aluminum prop,ty for any help.


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## dahut (Jun 21, 2016)

"Propellers are a voodoo science. Nobody really understands propellers."

- Allen Smith, professional prop builder, A.P.B.A. AND N.O.A. speed record holder.

"Many vessels enjoy little to no benefit from the use of stainless props. 
They are expensive, heavy, and exceedingly hard on the shifting system and gearcase (when not designed for the loads imposed by the SS prop).
...A runabout designed for 40 mph, or less, will gain little from a stainless prop.
The number of vessels that will NOT benefit from a stainless prop is legion, in fact. 
For the high speed bass boater, river racer, or out andout power professional, however, they are the way to go."

- John Fleming, from "Complete Guide To Outboard Engines"




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## dahut (Jun 21, 2016)

How much set-up adjustment have you done? With all the good you're getting already, a very minor change might do the trick.

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## DaleH (Jun 21, 2016)

dahut said:


> "A runabout designed for 40 mph, or less, will gain little from a stainless prop."
> 
> - John Fleming, from "Complete Guide To Outboard Engines


I'd agree with that 100%!

But check out the new 4-blade 'chopper' style (see picture below) aluminum props by Turning Point ... offering 'SS performance at an aluminum blade price', says their ads. I believe it, as just bought one and love it, gives 'sit pinning' acceleration at all aspects of the RPM range!

$100 or less delivered ... that one shown is on a 60hp motor.


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## dahut (Jun 21, 2016)

To be honest, I'm no propeller rocket scientist. I do know there are a zillion variables, though. 
Your prop looks cool, fer sure. It's great that it worked out for you.

It might be the OP needs a new prop.
Or maybe not.
Considering the downsides of SS, and the fact that so much is working right with his current one, well, I wonder.

Do dealers give loaner props, if you're buying from them?

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## scoobeb (Jun 22, 2016)

The prop on it now is in decent condition, no dings or barely any missing paint off of it. I have a 1648 flat bottom alumacraft jon boat if that helps so it doesn't take much to get it going. It gets good acceleration from the get go but I was wondering what the ss prop would do for it. I'm sure if I adjusted the height of the outboard a bit higher on the transom I could gain very,very minimal extra speed,a mph or possibly 2 at best due to eliminating all drag but I rather have it sitting on the transom for more of safety reasons, like the motor coming up,etc. The risk of lifting it is not worth the reward to me so I'm going a couple different routes,1 is going to a newer type of aluminum prop if maybe a cupped prop or something else that could help this boat get on plane just a hair faster. 2nd is I am in time going to buy a brand new advanced 25hp carb for it. I called a certain place who sells then for a great price and mercury is replacing the original 25hp carb with a better designed carb for overall performance and at the same price,so going from the 20 to 25hp carb would be a monster difference. I should gain at minimum a couple to possibly 5mph at wot and I should gain a good significant amount of extra torque out of the hole if everything goes according to plan. So maybe just a nice newer prop with the carb is the way to go. Best part is the carb takes literally minutes to take off and put on. So is a Solas aluminum prop and a turning point prop just as good or is one better than the other? I'm always willing to listen to any suggestions so shoot if have any. I do know that the way it is now is satisfactory but I know I can at least bust out a bit more torque and keep the same wot speed which is awesome to start with. This engine has just rediculous and insane power for a 24yr old merc. I can only imagine what a new good prop with the carb change would do. Ok,sitting back waiting on any info you guys may bring,thanks. Sorry,didn't mean to get all hyped up,I'm just excited about this outboard because it so far has exceeded all expectations and I want to get every ounce of power out of her I can. Ok,thanks.


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## dahut (Jun 22, 2016)

Have you asked a dealer to loan you different props to try? Or a buy-swap plan?
Does anyone even do that?
If you're buying, and not a time waster, maybe some will let you test 'em out first?
You sound like you know what you're doing, so maybe that's a possibility to further your cause.

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## onthewater102 (Jun 22, 2016)

When I went looking for a SS prop for my mariner (same size 2-stroke) the shop told me the stainless is only a benefit on large motors with a lot of torque that have enough impulse energy to cause the prop to flex - but any small outboard is not going to put out that kind of power & the only other benefit is the durability.

My issue was different - my prop was running very inefficiently according to the tach (approaching redline) and the GPS speed (far too slow for the size of the boat) - I ended up needing to have a cup applied to the edges of the blade and that fixed my issues. Cupping the prop gives it more bite in the water and has the effect of slowing it down. 

Before you start playing with props though get yourself a simple induction tach so you know where your RPMs are at with your current prop - it will give you an idea as to what changes you can make that will be safe for your motor.

 on a separate note I highly recommend the 25hp carb swap - so simple, affordable and so noticeable. I sourced mine from a newer Marathon series (mid-late 90's) 25hp through https://www.northernoutboard.com for $100 a year ago and it's an exact fit for my old '84 (early production of the '86-'90 models) - unbolt the old bolt on the new - couldn't be simpler. Here's a side-by-side comparison of the two - see how restricted the original carb throat is on the 20hp model on the left?


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## dahut (Jun 22, 2016)

> When I went looking for a SS prop for my mariner (same size 2-stroke) the shop told me the stainless is only a benefit on large motors with a lot of torque that have enough impulse energy to cause the prop to flex - but any small outboard is not going to put out that kind of power & the only other benefit is the durability.


Essentially what I alluded to in Mr. Flemings quote above.
But Mt. Everest is there to be climbed...

That really is a massive difference in carb throats! Wow!


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## RiverBottomOutdoors (Jun 22, 2016)

I've always been told that SS is more durable which makes it hard on gear case and shaft. Double edged sword.


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## dahut (Jun 22, 2016)

It's much heavier, too.

So every fast start ("outta the hole") puts a lot of inertia stress on the gearcase, and power head, trying to get that mass of metal going.

It also puts a lot of extra wear on the shifting dogs and gears each time you clunk that big chunk of metal in and out of gear.

And as you note, it'll take all the slamming into rocks and logs you can give it... but the gear case maybe can't.

The best way I can describe it is the SS prop has a limited use envelope where most users are concerned - but it is fashionable and very shiny.

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## scoobeb (Jun 22, 2016)

I will stick to an aluminum prop for sure,makes allot of sense to swap the carbs out though. I'm telling you from experience now that I have never ran a 20hp 2 stroke with the power this motor has,I mean it gets it. I have a 02 25hp 2 stroke mercury I'm running tomorrow morning to compare the hole shot and wot speed test. I bet the 20 Beats the 25. I have ran plenty of the late 90s to early 2000s models with the red decals and they were powerful but not like this 93 I have. My 93 20hp moved over 1000lbs of weight with ease 28.5+mph depending on wind and how flat or rough it is. I even hit near 30 a few times. With just me it hit near 30mph and that is with the standard 20hp carb, is that insane or what???? I think that is insane imo anyways,lol. I can't imagine what a carb swap would be like,wow is all I can say and excitement like crazy,I feel like a kid in a candy store, ha. My 24 yr old merc is like brand new to,low hrs,less than 30. The 02 I'm running tomorrow morning has,you ready for this,less than 3hrs,not one full tank of double oil for break in has even been ran through it yet. No matter what though I love this 93 style merc with the skinnier tiller handle and the sleek cowling design. I can't ever justify ever getting rid of it for any reason other than saving on gas. The only other motor I would put on my boat is a 20hp 4stroke suzuki or possibly a 25hp suzuki but I love how light the 20 is. I know I would lose some top end but the torque the 20hp suzuki makes is incredible for a 4stroke. It burns near no gas per hr and it will still push my 1648 near 26 to 29mph depending on weather. The suzuki is the closest thing to 2 stroke power in the portable range I have ever found. Just a sick motor and so technologically advanced for its time. So for now I will keep it until I get real world numbers on gas consumption compared to the suzuki. I will order a new aluminum 13 pitch Solas prop for my merc and in the fall my new carb. Thanks to everyone who is chiming in.


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## dahut (Jun 22, 2016)

Big difference what a well tuned, properly set up engine will do.
When you consider that the 2-stroke has twice the RPM capacity of the 4-stroke... I mean really think about that - it shouldn't be a surprise that it feels like a screamer.

Getting it peak tuned and then set-up right in the boats - well, that's the whole thing.
It sounds like you got it together; the stars are all aligned.
Congratulations!

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## beagler1 (Jun 22, 2016)

DaleH said:


> dahut said:
> 
> 
> > "A runabout designed for 40 mph, or less, will gain little from a stainless prop."
> ...



How does your cav plate sit level with such a small transom?


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## onthewater102 (Jun 23, 2016)

That's a little insane that you get those speeds out of a 1648 with the 20hp...I barely get 28 with my 1436 and just me in it. I did all my decking out of lightweight fiberglass & with the motor & TM removed my brother and I can still pick my boat up & carry it, so I know it's not that heavy. Do you have any decking in the 1648 or is it a bare hull? Also, were you the first owner of the motor or is it possible you've got the 25hp carb already courtesy of a prior owner? I gave you the pics of the two carbs - if you're certain you've got the 20hp I think I've got some more tuning to do, though I don't see how b/c it runs beautifully from idle right up to WOT even in the dead of winter.


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## scoobeb (Jun 23, 2016)

onthewater102 said:


> That's a little insane that you get those speeds out of a 1648 with the 20hp...I barely get 28 with my 1436 and just me in it. I did all my decking out of lightweight fiberglass & with the motor & TM removed my brother and I can still pick my boat up & carry it, so I know it's not that heavy. Do you have any decking in the 1648 or is it a bare hull? Also, were you the first owner of the motor or is it possible you've got the 25hp carb already courtesy of a prior owner? I gave you the pics of the two carbs - if you're certain you've got the 20hp I think I've got some more tuning to do, though I don't see how b/c it runs beautifully from idle right up to WOT even in the dead of winter.



Well 1st off my boat will plane much faster and better than a 1436 due to the planning surface being wider,that's just science.I have had a 1236/1436/1442/1542 and now a 1648 and out of all the boats this 1648 gets up on plane in a blink of an eye.I have a fiber glass floor.I got that stuff from home depot,it's like pvc board,won't rot,stain,break,etc......It's fairly light,it probably adds near 100lbs to the boat give or take a bit.I was running me at 300lbs,friend at 200lbs,boat is 320lbs,motor is 115lbs,plus full tank of gas (6 gal),a small cooler,plus the floor at near 100lbs,so i'm probably over 1000lbs total weight.This is why i don't want to get rid of this outboard,it has just some insane,crazy power and imagine what a 25hp carb will do.All speeds were taken like 20 times by gps because i couldn't even believe what kind of speeds i was getting.With the 1000lb load i was near 28.5mph constantly,with just me in the boat and nothing else i was at near 30 to 31mph give or take a mph going with the wind or against it and it was porpoising so bad i had to put my 150qt cooler in the front and add near 150lbs of blocks i had at my house and that stopped it finally.Like i said i have 2 gps's and i'm telling you the speeds are accurate but insane.I just bought a brand new 13 pitch prop so we will see how that does.The one i have on there now is in good shape but i want it as a back up.


I have the 20hp carb also,here is the pictures.


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## scoobeb (Jun 23, 2016)

Sorry they are sideways.


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## wmk0002 (Jun 23, 2016)

Man, you are right... that is straight screaming with a hell of a load. Do you know what your LU gear ratio is?


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## gunz (Jun 23, 2016)

I have had both and for what its worth here is my input. 

While I like the durability of SS I have damaged one beyond repair. Now I just run a quality aluminum and keep a spare . Still less invested than a quality SS prop and you have a spare on board in case you spin a hub or snap a blade. As mentioned it easier on the lower unit to run aluminum as well. 

This is not what everyone should od. but its what I do.


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## dahut (Jun 23, 2016)

scoobeb said:


> onthewater102 said:
> 
> 
> > That's a little insane that you get those speeds out of a 1648 with the 20hp...I barely get 28 with my 1436 and just me in it. I did all my decking out of lightweight fiberglass & with the motor & TM removed my brother and I can still pick my boat up & carry it, so I know it's not that heavy. Do you have any decking in the 1648 or is it a bare hull? Also, were you the first owner of the motor or is it possible you've got the 25hp carb already courtesy of a prior owner? I gave you the pics of the two carbs - if you're certain you've got the 20hp I think I've got some more tuning to do, though I don't see how b/c it runs beautifully from idle right up to WOT even in the dead of winter.
> ...


Maybe somebody put the wrong stickers on it- and it's a 40!

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## onthewater102 (Jun 23, 2016)

Yeah I wasn't comparing time to get on plane between a 1436 and a 1648 but once on plane I should be lighter and displacing less water with less contact surface area & all other things equal should if anything have a slightly higher top speed due to less resistance to the prop making the slip ever so slightly less...if nothing else the same top speed. :-( I guess perhaps my through hull side imaging transducer is really making that much drag. But sorry - didn't mean to hijack your thread...

That's definitely the same 20hp carb throat. I would hold off on the new 13P prop b/c if you're getting full RPM's out of your motor with the 20hp setup you'll be able to turn a more aggressive prop (14p or maybe even a 15p) with a 25hp @ the same RPM.


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## onthewater102 (Jun 23, 2016)

If you're not the original owner perhaps someone repitched the prop - that's also a possibility - you might already be running a more aggressive pitch & as the power output sounds sufficient to get it to full rated RPM's @ WOT. You'll know if you try the new 13P and go slower.


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## scoobeb (Jun 23, 2016)

I have used the same prop twice believe it or not. The 02 25hp I have has the same original prop on it,same numbers and I switched them out and got exactly the same speed. I was thinking of going to a 14 pitch prop but I thought my hole shot would suffer some even know it gets on plane I mean instantly. The lower unit ratio is possibly what's having me be able to get this speed,it's 2.25 which is an awesome LU gear ratio imo. Funny thing is both mercs have the original props on them,the 93 I have has all of 25hrs of use since new,the old man who owned it used it for like a yr here in fl and passed away and it sat in storage for a very long time,near most of it's life,the guy I got it from was his son like 22yrs later,how crazy is that??? The 02 merc has 3hrs of use,never had a tank of gas ran through it yet and it sat for near 14yrs,it's like new except a few scratches ,I'm selling the 02 and keeping the 93 because I put a bunch of work into it,just maintenance stuff. It is I mean a sweet engine,both are so clean you can eat dinner off them,lol.


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## scoobeb (Jun 23, 2016)

I just ordered a new 13 pitch Solas aluminum prop and I'm going to use the one on it as a spare,I may get a 14 pitch when I swap carbs out in the fall,I may do it earlier but will see. My buddy has a brand new 20hp Tohatsu, he has the same boat as me and he gets on plane a bit faster than me with a 4stroke believe it or not,he's also carrying 600 lbs of weight compared to my over 1000lbs,now granted his 20hp is just that as mine is off a 25hp power head so a big difference, he can actually get me out of the hole but in seconds I'm blowing by him and he couldn't believe how fast I caught up to him because he was a good 15ft ahead of me. I was totally impressed with the torque of that 20hp 4stroke Tohatsu, blew my mind. I have owned a new 20hp 4stroke suzuki as well and the torque on that motor is insane as well for a 4stroke. Keep in mind though,my buddy is running a 10 pitch prop so he should get me out of the hole because I'm running 3 sizes bigger but he was just amazed at how much power my 20 had to catch him. I was two. I get on plane in seconds,he gets on plane in like micro seconds if their is such thing,lol. These 4strokes are starting to compete a bit on power with the 2 strokes in amazement. Good to know our future for 4 strokes looks bright.


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## ericman (Jul 11, 2016)

I'd say that an aluminum prop on a 20 hp is NOT flexing when under power. I'd also say that the only time a stainless prop really makes ANY sense at all is on a much bigger motor, used in deep enough water to avoid hitting anything with the prop OR in saltwater. If you hit anything with the stainless prop, especially when running a 20 hp with a 1/2" driveshaft, you will severely mess up your drive shaft, whereas the aluminum prop will bend or break, which is a much cheaper fix than a new driveshaft.


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## scoobeb (Jul 17, 2016)

I just went with a new aluminum prop and i will use the original one as a spare.


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