Distinguishing aluminum and stainless steel prop?

[sweetmarie]

I think I'm going to get thrown to the lions for this question but here goes. I wanted a second prop as a spare and thought I'd go stainless and keep my already owned "aluminum" as a spare. Running a 1986 Evinrude 175 hp on a 175 Doral Spirit. Well after searching, I find out that the prop I have now (# 389923) is listed as a stainless steel prop.
Now this prop is nowhere near a new prop so it doesn't shine like my neighbour's new toy, his s/s prop could blind an already blind man. My stupid question is, without the superb shine, how would I have know that my prop is s/s other than the model # ? Magnets don't stick to either.
Probably by the weight but without an another prop to compare?

 

[Don S]

Re: Distinguishing aluminum and stainless steel prop?

Weight. Aluminum props don't weigh near what a SS prop does.

 

[sschefer]

Re: Distinguishing aluminum and stainless steel prop?

As Don say's the weight is how to tell the diff if you have a known al prop to compare it to. However, if you just tap one of the blades with a 16 penny nail the stainless will ring and the al with not.

 

[sweetmarie]

Re: Distinguishing aluminum and stainless steel prop?

As Don say's the weight is how to tell the diff if you have a known al prop to compare it to. However, if you just tap one of the blades with a 16 penny nail the stainless will ring and the al with not.

Thanks, had to google for what a 16 penny nail was, lol.

 

[scooper77515]

Re: Distinguishing aluminum and stainless steel prop?

OK, so what is the big thing about stainless? I know, should start a new thread....I have two aluminums, and other than pitting easily from rocks and stuff, I see nothing wrong with them. And they are weak, so they will hopefully break before they take out something more expensive higher up on the drivetrain, should I hit something.

So what is the allure for stainless props?

Again, likely a simple question, send the lions on over. Just converted over from jet boats last summer, so boating since age 3, but still a newbie at age 38...

 

[wifisher]

Re: Distinguishing aluminum and stainless steel prop?

Another way to tell is to take a nail and scratch the surface. If it is aluminum, it will dig in. On SS it will not.

The weight difference is pretty significant though.

 

[sweetmarie]

Re: Distinguishing aluminum and stainless steel prop?

Another way to tell is to take a nail and scratch the surface. If it is aluminum, it will dig in. On SS it will not.

The weight difference is pretty significant though.

When you have only one prop, you can't compare unless someone can tell me how much my prop should weigh? The scratching method sounds logical.

 

[sweetmarie]

Re: Distinguishing aluminum and stainless steel prop?

OK, so what is the big thing about stainless? I know, should start a new thread....I have two aluminums, and other than pitting easily from rocks and stuff, I see nothing wrong with them. And they are weak, so they will hopefully break before they take out something more expensive higher up on the drivetrain, should I hit something.

So what is the allure for stainless props?

Again, likely a simple question, send the lions on over. Just converted over from jet boats last summer, so boating since age 3, but still a newbie at age 38...

Take it for what it's worth but I just read today that unless you're going to be cruising 50 mph and above, the ss prop may be helpfull. My cruising speed is nowehere near that (I'll do it to clean out cobwebs now and then) so I think I'll stick to aluminum.
Can someone attest to the 50+ mph law?

 

[sschefer]

Re: Distinguishing aluminum and stainless steel prop?

Aluminum props flex so you will loose performance in bottom end, turns and top end. When just cruising there's not a hole lot of difference. Because of the flex, no one bothers to try to tune them like they do with a stainless prop.

 

[wbc1957]

Re: Distinguishing aluminum and stainless steel prop?

The 389923 is an OMC Stainless Steel prop number. It should be a 14 1/4 x 21. OMC props are normally teflon coated Stainless Steel props, so sorry, no shine! The standard Aluminum prop that would have been suggested with a package that included your 399923 Stainless prop, would have been the 391201 14 1/2 x 19 prop. Both of these props are pretty common for the horsepower range you are showing in your initial question, and easily replacable on ebay etc.... Plus, iboats sells a great 4 blade Solas prop in both Stainless and Aluminum, which will provide a better hole shot. But, your current Stainless 389923 is considered the optional 3 blade speed prop for the horsepower range.

 

[steelespike]

Re: Distinguishing aluminum and stainless steel prop?

ss props will attract a magnet some slightly others more.al no attraction at all.

 

[steelespike]

Re: Distinguishing aluminum and stainless steel prop?

OK, so what is the big thing about stainless? I know, should start a new thread....I have two aluminums, and other than pitting easily from rocks and stuff, I see nothing wrong with them. And they are weak, so they will hopefully break before they take out something more expensive higher up on the drivetrain, should I hit something.

So what is the allure for stainless props?

Again, likely a simple question, send the lions on over. Just converted over from jet boats last summer, so boating since age 3, but still a newbie at age 38...

Exactly, if you run where hard contacts(rocks)is likely stay away from ss.If mud or sand ss may hold up longer.
ss will likely provide accross the board improvement though could be a few tenths to a few mph,sometimes several mph.likely when an al prop is under performing.
There are al props that provide close to ss performance.Turning PointHustler is one and Turning Point Rascal for smaller outboards 25-40 hp.

 

[Robbabob]

Re: Distinguishing aluminum and stainless steel prop?

FWIW

My SS (14.25X21) weighs approximately 13 pounds, +- the floor scale difference with me holding the prop.

 

[81 Checkmate]

Re: Distinguishing aluminum and stainless steel prop?

The best thing would be to take it off and that will tell the story. By the weight in your hand!!!!!
S/S is far more heavier that alum.
Plus it will teach you how to do it.

 

[sweetmarie]

Re: Distinguishing aluminum and stainless steel prop?

Thanks to all for your info, prop weight, prop performance and sizes, etc. Great help.

 

[scooper77515]

Re: Distinguishing aluminum and stainless steel prop?

And thanks for the info on stainless vs aluminum performance.

So far, no issues on my lake, until last weekend, sucked up a bunch of small rocks pitting my blades a little, cuz the lake is down WAY down. We have stumps I worry about more, and my current aluminum props are working fine, so I will live with them. Cheap to have re-shaped and balanced when/if I hit something.