PROPELLERS: Alumimum VS Stainless?

Question

I'm thinking of changing my 3 blade aluminum propeller to a 3 or 4 blade stainless steel propeller.
Should I change the pitch or keep the same pitch as the aluminum?
They claim that stainless cuts through the water much easier than aluminum - this makes me wonder about the pitch - Should I lower the pitch or add some pitch?

Ron.

Answer 1

First, water density doesn't change because it's not as afraid of aluminum as it is of stainless so neither one "cuts" the water and better than the other. Stainless is just thinner so people assume it runs better through the water.

Second, changing from 3 blades to 4 will cost you some speed but improve power. Check out speed props, they are mostly 2 blade to keep down cavitation.

Third, check the manufacturer's web site or go to a marina that deals with your motor and ask what they recommend, don't take our word for it or you will end up spending a fortune before you get what you want.

Also, hitting stuff with either prop won't make any difference, it isn't the prop that absorbs the impact it is the core or the shear pin that will save the lower unit. This is going to potentially cost you quite a few bucks so go to a subject matter expert, not the yahoo goobers.

Answer 2

Some boat dealers "may" have test props, I know years ago the place I worked for did. Try before you buy.
I guess Stainless have a lot of advantages over Aluminum, but, I have always used Aluminum as they cheaper and I can have a few different pitches, depending on what I want to do. The main thing you need to be concerned with is your WOT RPM (Wide open throttle). If, you go with too high a pitch, you not get up the RPMs. Too low you can compromise by throttling back.
Maybe the links can help;
http://www.caravelleboats.com/propeller%20info.htm
http://www.rundquist.com/how_change_pitch.htm

Answer 3

your aluminum prop is probably not cupped. if it is right for your boat, don't go straight across to a stainless with the pitch. SS props are cupped. drop 2 inches of pitch and at that point it won't matter if it's 3 or 4 blades. 4 blades just dampens the vibration basically.

Answer 4

Personally I use stainless steel for my own dogs because ti is easy to keep clean, and doesn't weigh too much when I am carrying 3 large bowls full of food. Plus when I drop them they don't break. The only reason I don't use plastic is because my dogs like to chew anything plastic :P I use plastic for my foster cats and foster puppies and have never had any sort of infection. Personally I think that is some sort of myth as I have never known anyone's pet to get an infection from a plastic bowl. As long as you keep them clean, plastic or stainless are both fine

Answer 5

Supposedly you will pick up a little more speed with a stainless prop
But there are draw backs also. If you hit something with your prop an aluminum is more forgiving it will bend or break
Stainless props are harder to bend and break .The end result is damage to internal parts in drive such as twisted splines and gear fracturing.

Answer 6

I alway's run an aluminum prop, as mentioned above, you'll just bend the prop up if you have a "Prop Strike", A "S/S" prop will let the shock of hitting the obstruction go right up the drive train damaging the internal parts of the outboard.... A bent prop to replace, or a busted up crank shaft, and a lower unit..?.... gee, another "Tuffy" !

Answer 7

call 301 442 7724

Answer 8

hope this is of some help mate.

http://www.rbbi.com/folders/prop/propcalc.htm