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Aluminum vs stainless steel prop

of what I understand about pro

of what I understand about props (not much) but the SS doesn't flex like the aluminum prop will which will give you more bite in the water.. but a downfall to the SS prop (as I found out the hard way) is that if you hit something in the water (like a floating Log at night) the aluminum prop will bend or break and the SS prop will stay strong and possibly mess up your shaft or worse gears and such..
 
"Well said Bill

Aluminum p

"Well said Bill

Aluminum props are cheap, they have flex issues (thats why you never see them in high performance situation).

However they will act as a safety valve in most occasions and will cause their own demise by absorbing the the forces created in a high speed impact before those forces can be applied to the gearbox.

You can do yourself a little test, if you can find a bit of aluminium and a bit of stailess the same size, say a couple of feet long, then using the same force holding the two pieces in each hand strike something hard with them, if you compare the jaring sensation you get between the two metals the stainless will be greater, the same type of force is applied when your prop hits something submerged in the water.

Thats why aluminium props break and stainless props break things they are attached to.

Stainless is great as far as I am concerned as long as you do not hit anything, the only other problem that can be associated with stainless props is a possible increase in galvanic corosion.

As to wether you need to go down a size in pitch or not if you go to stainless you first need to decide is there a problem with the pitch you are running now, is it the best for your particular application.


Cheers
Peter C"
 
"Gerald, You should be able t

"Gerald, You should be able to use the same pitch, provided you stick with the same kind of prop (same diameter, same num of blades)."
 
"OK here it is I did a little

"OK here it is I did a little test today. I got a SS prop the same size as the aluminum one that is on my boat now, went out to the water and did four test runs with each prop. 2 up the bay and 2 back down the bay (with each prop) trim was set the same the whole time..

SS Prop ran 4000-4300 RPMS WOT
Alum. Prop ran 4200-4500 RPMS WOT
RPMS on a Digital Gauge.

Also the SS prop seemed to take longer getting out of the hole and up on plane..

well I hope this helps and answers your questions.."
 
I think your test was a good s

I think your test was a good start. Same prop specs? Same pitch & diameter; both cupped?

What is the power plant on your boat?

Try running the test again and trim the prop to max the RPMs on the first run. Don't change the trim and run it again from the hole. See what you get.
 
"Bill
If you can do as Guy ha

"Bill
If you can do as Guy has suggested that would be great, its a good comparison you have done.
Peter C"
 
"Guy,
I have a 97 21ft cuddy

"Guy,
I have a 97 21ft cuddy cabin with a 5.7L 210HP Mercruiser
before the test I found the perfect trim setting and made a mark on the gauge so I could put it back to the same point every time that I had to raise it to change the props. both props were 14x21 and cupped. I took my Aluminum prop with me to the shop and they matched them up for me just to make sure they were the same.."
 
One other thing was the SS pro

One other thing was the SS prop seemed to keep the bow higher in the water also..
 
"Bill:

Do you think the rai

"Bill:

Do you think the raised bow is because the SS prop was not flexing like the aluminum prop? I have a (spare) alum. prop that came w/my boat. It's a 19' 1987 Baretta Sportster w/4.3L 2 BBL non-vortec 175 HP. I bought a Michigan 21 pitch 15.25" SS prop. from a huge prop dealer in Cincinnati, OH that had it in a box on the shelf for 18 years. He stated, after I old him what boat I had, he thought he had one just for the yr/model engine/OD I had. I paid $225 for it and have laughed all the way home with the deal I got.

When I start out of the hole the RPMs jump at 1/2 throttle to 2500 RPMs and before it reaches 3000 RPMs it is on plane and approaching 25 mph. By the time it reaches 3500 RPMs it is cruising at 30 mph and now trimmed up/out at WOT it is doing 42 mph at 4400 RPMs on smooth water. Loaded wt. is approx. 4000 lbs. The old alum. prop never does that."
 
"Bill;
Interesting test resul

"Bill;
Interesting test results.
I wonder if the difference in RPM is because of the flexxing of the aluminum?
Did you get any WOT speeds to compare?
It sounds to me like you could go down 2" of pitch on the SS prop, regain your hole shot, and get your RPM nearer to book WOT numbers, and maybe have a higher top speed.
Did the SS prop have the Flo tork inner spline system? If so, that will help to save your shaft and gears from impact damage if you have an inadvertent prop strike.
Rod"
 
"Bill;
One other difference b

"Bill;
One other difference between aluminum and SS props; the SS prop is much more expensive to repair. Like double, or more.
The voice of sad experience talking.
Rod"
 
Due to forget to bring the ol

Due to forget to bring the ol GPS unit I wasn't able to get a top speed report and my speedo jumps like crazy no matter how many times I clean out that little hole in my outdrive (alpha one).. about the performance of SS props I did try one last year I think it was a 14.5 x 19 and it did great couldn't be more happier with the results until that log ended my day and my outdrive.. since then only aluminum on my boat..
 
Bill;
You should try removing

Bill;
You should try removing the speedo tubing at the back of the head and blowing it out back to the drive. Sometimes they fill with water and they need to be full of air to cushion all the pulsations in the water.
I hear ya on the aluminum prop. Best of luck.
Rod
 
"One more AL advantage over SS

"One more AL advantage over SS: THey shift easier. The weight of an SS prop (and bronze is even heavier) pounds the shifting mechanism more than a lightweight AL prop. My Mark 35A (4 cylinder OB) shifts effortlessly with an AL prop, and slams into gear with a bronze.

Jeff"
 
FJ:

Good point. Do you thi

FJ:

Good point. Do you think SS props shorten the life of the shift mechanism parts?
 
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