I am thinking of getting a new propeller for my boat...?

Question

But I don't know much about them! Currently I have a three blade aluminum prop on a 22 ft SeaRay (inboard/outboard, Bravo One mercruiser). Are there significant performance benefits to changing to a stainless steel prop? How about different blade numbers? We use the boat for water skiing, tubing, etc, as well as driving to and from our cottage; it is already such a pig on gas, I'm not worried about using a little more.

Thanks Doane...I don't need to go much faster than 35 mph, and being able to reverse effectively is important.

Answer 1

The starting place for prop selection is RPM at wide open throttle (WOT); on an outboard, WOT is generally 5200 - 5800 RPM (check your manual, as it may be different on an i/o).

A prop with a higher pitch will produce more torque (better for pulling out skiers) and will lower your WOT RPM. Likewise, a prop with a lower pitch will increase your WOT RPM. Statements like "higher pitch gives you better mileage" will be generally false, as you need to select the prop that gives you the appropriate WOT range. Usually, 1" increase of pitch will decrease your RPM by 200.

And YES, I know you are not always operating the engine at WOT, but this is your baseline and therefore affects all other areas of your range of throttle.


Stainless Steel props do flex less than aluminum, and are therefore generally preferred for ski boats, as they transfer more power to propulsion rather than to deforming the prop blades. However, be careful with a stainless prop if you generally boat in a shallow area with a rocky bottom, as SS props will NOT bend if they hit something; instead, it will destroy your lower gearcase. An aluminum prop will be a better choice as they are usually less than half the cost of SS, and will sacrifice themselves before transferring damage to your lower unit.

That said, I live in a very shallow area with a muddy, sandy bottom and use a SS prop and don't worry about it.

Answer 2

why change the prop.... If it ant broke just get a spare... SS props are more durable yes... but are they worth the price. The same prop same pitch ss or aluminum it doesnt matter. They will all perfr the same.. Flexing is not a problem. The alluminum is softer and more prone to damage if you hit something... I ran a 150 hp merc on a21ftcenter console and had no problems.. The prop was fine... at each service it was checked and it was true in shape .,
I asked a bout a SS prop.... Yep they are harder wearing may last longer but if you hit a rock .. the bottom yep they take the bash and dont bend but where does that energy from the hit go..... Its transfered up your prop shaft into the motor.. A friend of mine adamanet about ss props .. is just having anew prop shaft fitted to his 175 johnson... he hit a rock... small chip on prop but bent up the prop shaft.
He said if it was aluminum the blade whould have bent but at least its less expensive for a alluminum prop..

Answer 3

I run nothing but SS as they are more durable an don't flex when skiing. you can try a 4 blade as it's smoother $$$ is your boat turning full rpm awot loaded fuel & gear if not than drop 1 pitch or if over rpm than go up 1.There are thing you can do if carbered not EFI

Answer 4

You also need to be concerned with the "Pitch" of the prop and which direction it turns.

There would be no performance difference between st stl or aluminum. St stl lasts longer.....