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PROP - Aluminium or Stainless

Posted: Sun Oct 11, 2015 9:51 am
by Wind Chime
Our main aluminium prop has a few dings and twists in it from years of regular use so am considering taking it in to get refurbished, but was also thinking maybe put the repair money towards a stainless prop. I have the correct pitch and diameter for our load.

Thought I would run it by everyone about what you use and why?

Pros for both Aluminium and Stainless Steel;
Aluminium pros - cheaper, softer so dings bend prop not shaft.
Stainless pros - better performance, last longer.

What do you have?

Re: PROP - Aluminium or Stainless

Posted: Sun Oct 11, 2015 10:19 am
by miamistyle
I don't think you would notice a large enough performance improvement with a 50hp to justify the extra price.

I bet very few folks with macs run stainless props.

Re: PROP - Aluminium or Stainless

Posted: Sun Oct 11, 2015 11:25 am
by dlandersson
Anther consideration is where you sail - the kind of obstacles in the water. 8)

On the south side of Lake Michigan, there really aren't any stumps, rocks, etc, so I have a stainless (and I have several aluminium). One season I played around with props quite a bit. :)
Wind Chime wrote:Our main aluminium prop has a few dings and twists in it from years of regular use so am considering taking it in to get refurbished, but was also thinking maybe put the repair money towards a stainless prop. I have the correct pitch and diameter for our load.

Thought I would run it by everyone about what you use and why?

Pros for both Aluminium and Stainless Steel;
Aluminium pros - cheaper, softer so dings bend prop not shaft.
Stainless pros - better performance, last longer.

What do you have?

Re: PROP - Aluminium or Stainless

Posted: Sun Oct 11, 2015 4:41 pm
by NiceAft
dlandersson wrote:Anther consideration is where you sail - the kind of obstacles in the water. 8)

On the south side of Lake Michigan, there really aren't any stumps, rocks, etc, so I have a stainless (and I have several aluminium). One season I played around with props quite a bit. :)
Wind Chime wrote:Our main aluminium prop has a few dings and twists in it from years of regular use so am considering taking it in to get refurbished, but was also thinking maybe put the repair money towards a stainless prop. I have the correct pitch and diameter for our load.

Thought I would run it by everyone about what you use and why?

Pros for both Aluminium and Stainless Steel;
Aluminium pros - cheaper, softer so dings bend prop not shaft.
Stainless pros - better performance, last longer.

What do you have?
One season you played around with props quite a bit...................aaand what :?: Is this your version of a pregnant pause :?: :?: :P :D

Re: PROP - Aluminium or Stainless

Posted: Sun Oct 11, 2015 5:34 pm
by dlandersson
Actually no, one season (my second) I focused on props, getting several and changing them often. Got an inexpensive (cheap, really) inflatable I used to tied off on the rear of my X and swap out props. Hint, do it in the early am, before it gets hot. :P

FYI, I have a 97 X with a 50 HP Merc (non-bigfoot). Any suggestions on which 4 bladed prop I should think about getting? More interested in hauling my kids (tubing) than in getting 20 mph. :)
NiceAft wrote:
dlandersson wrote:Anther consideration is where you sail - the kind of obstacles in the water. 8)

On the south side of Lake Michigan, there really aren't any stumps, rocks, etc, so I have a stainless (and I have several aluminium). One season I played around with props quite a bit. :)
Wind Chime wrote:Our main aluminium prop has a few dings and twists in it from years of regular use so am considering taking it in to get refurbished, but was also thinking maybe put the repair money towards a stainless prop. I have the correct pitch and diameter for our load.

Thought I would run it by everyone about what you use and why?

Pros for both Aluminium and Stainless Steel;
Aluminium pros - cheaper, softer so dings bend prop not shaft.
Stainless pros - better performance, last longer.

What do you have?
One season you played around with props quite a bit...................aaand what :?: Is this your version of a pregnant pause :?: :?: :P :D

Re: PROP - Aluminium or Stainless

Posted: Sun Oct 11, 2015 5:53 pm
by Terry
The most economical route is to have your current prop refurbished $50-$100 tops. There is a shop on Minoru Blvd in Richmond just behind the MV branch where I took mine.
A new SS prop will set you back a few hundred bucks!!
That said, there are still some things to consider. I have heard that SS will give you better performance, maybe even add some pitch because it is thinner. Also heard that being heavier it might take more energy to spin, not sure I believe that though. I do believe better performance though, maybe more speed. They can still be damaged though depending on what they hit. If I had the extra cash I might try a SS just to see what it can do. Being SS they would not flex as much as an aluminum one and being thinner they have less resistance in the water. Unfortunately the extra cost is more than the return you get in performance.

Re: PROP - Aluminium or Stainless

Posted: Mon Oct 12, 2015 5:37 am
by Tomfoolery
Terry wrote:Also heard that being heavier it might take more energy to spin, not sure I believe that though.
As well you shouldn't. If it's got more mass, and the same geometry, it's got more rotational inertia, so it will take more energy to increase its speed (which it returns when you decrease its speed). But once it's running at a steady speed, it takes zero additional energy to keep running at that speed, not counting the work it's doing, of course (pushing the boat). It's a flywheel, and a rather puny one at that, even at 2000-2500 rpm.* Maybe a driver can feel that in a high performance racing boat when changing throttle settings, but not in a Mac with an outboard. So the fraction of a second it takes to go from idle to near-full throttle speed isn't going to change in any noticeable way with a heavier prop.

*The inertia of a spinning mass through a gear train changes as the square of the ratio, so a prop running at 1/2 the speed of the engine has 1/4 of the inertia reflected to the flywheel of the engine. So the prop inertia is quite puny compared to the flywheel and crank of the engine, and even then, it only matters when changing engine speed, not steady running.

Re: PROP - Aluminium or Stainless

Posted: Mon Oct 12, 2015 6:39 am
by Russ
Aluminum props are much cheaper to repair/recondition. I chewed up a few on my runabout. Amazing how they can fix these things.
SS cost MUCH more to repair.
So far on our Mac, I've never damaged a prop.

SS props are also shiny and cool. I'd be curious side by side what performance difference there are.


--Russ

Re: PROP - Aluminium or Stainless

Posted: Mon Oct 12, 2015 7:11 am
by Tomfoolery
RussMT wrote:SS props are also shiny and cool.
And if your boat lives on a trailer, much more tempting to a thief. :cry:

Re: PROP - Aluminium or Stainless

Posted: Mon Oct 12, 2015 7:35 pm
by yukonbob
If you've dinged your alum prop where you sail that should be something to consider along with the repair costs mentioned above. Hitting objects with the harder ss prop does increase the possibility or damaging your lower leg or even the drive shaft. The softer alum prop will help absorb more of the impact. IMO Id be concentrating more on pitch performance than material performance.

Re: PROP - Aluminium or Stainless

Posted: Mon Oct 12, 2015 9:04 pm
by Russ
yukonbob wrote:If you've dinged your alum prop where you sail that should be something to consider along with the repair costs mentioned above. Hitting objects with the harder ss prop does increase the possibility or damaging your lower leg or even the drive shaft. The softer alum prop will help absorb more of the impact. IMO Id be concentrating more on pitch performance than material performance.
That's an interesting point. The AL prop is somewhat sacrificial isn't it.
However, knock on wood, both my AL props are in perfect condition. Now I've gone and jinxed myself.

--Russ

Re: PROP - Aluminium or Stainless

Posted: Tue Oct 13, 2015 3:30 am
by Erik Hardtle
Here is why I will never go to stainless steel:

Image

Rocks vs Prop: Lower unit damage= NONE.

I don't blame the prop... just the capt. :|

Re: PROP - Aluminium or Stainless

Posted: Tue Oct 13, 2015 4:14 am
by dlandersson
I'm looking at 4 bladed props. Is your outboard a 50 HP Merc? 8)
Erik Hardtle wrote:Here is why I will never go to stainless steel:

Image

Rocks vs Prop: Lower unit damage= NONE.

I don't blame the prop... just the capt. :|

Re: PROP - Aluminium or Stainless

Posted: Tue Oct 13, 2015 5:45 am
by Jimmyt
Looks like he was running about 2-3/8 blades... I would guess a slight dip in performance after that mod. Ouch!

Re: PROP - Aluminium or Stainless

Posted: Tue Oct 13, 2015 6:31 am
by miamistyle
I can tell you that you only need one blade to make it home! :?