Stainless Advantage - The Hull Truth

guanacay · 08-27-2002, 11:19 AM

What performance advantage would be achieved by switching to a good stainless prop on a 19.5 CC with a 115hp 2-stroke? Hole shot, top speed? Would it be worth it? The boat goes 45mph right now.

Scott Meier
The "Dan"Forth

LI Sound Grunt · 08-27-2002, 08:06 PM

gusssing no top speed if you stay with the same pitch/size

little more hole shot response

don't do it

aint worth it if you hit sometinng and blow the lower unit instead of a cheap propeller

MarkA · 08-27-2002, 09:48 PM

Guanacay,

Stainless props offer more performance for two reasons: 1)design, 2)composition.

Good quality stainless propellers are generally engineered and manufactured to closer tolerances than aluminum props, and many feature performance enhancing design properties such as blade rake and cup that will give particular propellers certain performance advantages. For example, a highly raked and cup stainless propeller of a similar pitch to a mickey mouse eared OEM propeller will offer more stern lift and flatter response. Quality stainless propellers are often offered in four or five blade designs, which by their nature offer distinct advantages and drawbacks, depending on application.

As far as composition goes, stainless lends itself to being cast with thinner blades, is more rugged and maleable than cast aluminum, and seems to offer more balance than similar aluminum designs. Stainless is the premium propeller manufacturing medium. The rigidity of stainless offers more efficiency in transferring power from the engine to the prop to the water because it flexes less. Alot less.

Stainless propellers offer some common disadvantages, that being of weight (a 13.75 x 15 might weigh ten pounds, and aluminum might weigh three), and rigidity. The very rigidity that makes them perform well is a problem if you whack something hard, the force is transferred to the output shaft, but it is also in aluminum, your aluminum propeller is much more likely to fold than the steel. Stainless props feature slip hubs like the others, so that mitigates the danger somewhat. The stainless prop will also hold up much longer if you run in shallow water and touch the bottom know and then. One encounter of a shoaly bottom is enough to really damage an aluminum propeller, the stainless shrugs that off pretty well.

Because of the differences in performance and the more agressive designs of the stainless props, you may have to drop in pitch, but only a trial will tell you that. With severe raking and cupping, you can expect to step down two inches in pitch.

Give one a try, you may find one that gets you a couple of MPH top end, a better hole shot, and better handling all around.

Mark

MarshFisher · 08-27-2002, 10:15 PM

Mark,
Great answer! Learned a lot. Thanks,
David

capttangles · 08-27-2002, 10:28 PM

The main thing to be gained by using a stainless prop is better boat handling especially in tight turns. They seem to take a better bite in turning manuevers and your stern doesn't slide out. They are also more resistant to minor groundings. Naturally if you hit anything hard enough either the prop or lower unit can suffer damages but damage is more likely to occur with an Aluminum prop than with a stainless one. Even after a few submerged logs my stainless props are like new. I would have gone thru at least 4 aluminum ones by now!

Spooled · 08-28-2002, 07:05 AM

I was(am) still trying to match up a prop to a 23 Key West CC with 225 yamaha ox66. Main problem was needed more bow lift. Fitted a stainless and got the bow lift(able to trim motor more without cavitation I guess better grab) but RPM went from 5200 to 5000. Going to go down a size and see what happens from there. Using Yamaha SW series.

LI Sound Grunt · 08-28-2002, 07:32 AM

Spooled

I think "bow lift" is more a function of trim. Although I may be all wet here - haven't heard that term and assuming you are bow down "plowing" and want to get a better attitude and get the bow higher or out of the water.

Probably trim tabs or motor trim will do more than a different prop.

Spooled · 08-28-2002, 12:29 PM

LI

This was how it was explained to me. I am able to trim the motor up higher without the cavitation(more Grab? Torque?) which gets the bow up while still under control-per the factory rep. Before I could only go 2 bars on yamaha tilt guage before cavitation in a bouncy sea. Now can go 4 bars. Lost RPM's from 5200 to 5000 fully loaded so looking to get into the 5500 light load 5300 full load. Not sure about the tech stuff just trying to best performance #'s