Stainless Props on small motors - good, bad, ugly?

Am considering a new prop for my 1985 15 HP Johnson. This will go on a StarCraft Kingfisher, which is a semi v-hull about a 1652. I plan to set it up as a tiller rig. Prop material options include aluminum and SS. When it comes to SS props, I and am not able to figure out if the negative talk ("too heavy" "hard on lower units", etc. ) is reality or just an internet myth. To my logic, if they are so terrible, why make 'em? So am looking for firsthand knowledge on the topic, with appreciation in advance..

Thanks!

When I looked into them for my 25hp 2 stroke I found they are used to prevent distortion of the prop due to the torque of the motor, and that they are totally unnecessary on small motors as these motors do not generate the amounts of torque required to distort an aluminum prop. Stainless props do weigh more, so it is more inertia your motor has to rotate which, if nothing else, will reduce performance. Whether or not this extra rotating mass translates to more wear and tear I can't say, but it certainly won't result in less.

I run stainless on all my smaller motors (25-40 HP) I fish in snaggy stumpy water. The only reason I do is I get tired of buying props. You hit a limb as big as your thumb with an aluminum it is either rolled over or has a chunk knocked out of it. Stainless it doesn't touch.

As to the wear and tear on lower units I have been using them for over 25 years on OMC, Mercury, Zuks and now Yamaha and have yet to bust a gear, housing or shaft.

I run an F 115 in the salt in south Jersey, the shallows shift from yr to yr so running aground is not unheard of and polishing ones prop is done regularly. I've run hard aground at 35 MPH without an issue on my lower unit or SS prop.

A little heavier but if you hit chit and need to change an aluminum prop I'd change for SS. If you have an alum. prop keep it until it fails. If you feel there's a low risk of damaging one pick out another one.

nccatfisher said:

I run stainless on all my smaller motors (25-40 HP) I fish in snaggy stumpy water. The only reason I do is I get tired of buying props. You hit a limb as big as your thumb with an aluminum it is either rolled over or has a chunk knocked out of it. Stainless it doesn't touch.

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A new, low co$t option for smaller HP motors (40hp thru V4s) are the pressed aluminum blades by Turning Point. It's a new process akin to forging that results in aluminum blades almost as thin as SS ones. Their new proprietary process is called 'squeeze casting' and unlike die casting, this method further compresses the blade for a tighter grain structure, making them both thinner and stronger.

I run a 4-blade one on my 60hp Evinrude and it's impressive! Only $100 too! And note Turning Point has a prop exchange process, so you never get stuck with a prop you can't use.

SS is much stronger than al. This lets the manufacturer make SS prop blades thinner than AL props, which reduces drag while it's spinning in the water.

As a "general rule" SS will go a little faster if all else is equal-and it rarely is. You can pull a stock AL prop off of a brand new motor after getting a baseline, slap on your favorite SS prop with the same pitch and it might help or it might hurt. These smaller motors are more sensitive to propping than, say 90hp and larger motors. 4 stroke engines are more sensitive to propping than 2 stroke motors are if they are the same HP. The "early" (mid 1990s or so) 4 strokes even more sensitive than these newer ones. Thus it's really imperative to get the RIGHT prop for your small 4 stroke motor. Generally speaking a 2 stroke motor can "get away" with a mismatched prop more than a 4 stroke would. Notice I said "generally"....not every motor is the same, and obviously not all props are the same either.

it's also possible to take a run of the mill SS prop and send it off for blueprinting, and pick up a mph or two or three. But when this is done, the blades sometimes get thinner and more sensitive to bending and/or breaking (yes you can break an SS prop).

Deflection is a non-issue on props smaller than about 12" in diameter and thus about 75hp and smaller.

Most aluminum props that come factory installed are a good compromise between speed and holeshot. If you're not a racer, usually the stock factory installed prop will do everything you need.

Some factory installed stuff is better quality than others as well. I've seen brand new suzuki's break a blade off at a hint of a strike with the equivalent of a stick in the water; but circumstances are different for everyone, everyone's motors, and everyone's operating style. Some guys seemingly intentionally try to destroy good equipment, others can't help it, and some never have a problem. I will say this: Yamaha's stock aluminum "white" props-especially on the 25's-are thin blades and they bend fairly easily. Don't hit anything and they won't bend but sometimes I know that it's unavoidable.

SS props are cupped on the trailing edge. This gives lift, lift raises more of the hull out of the water at cruise, less hull in the water means less whetted surface and less resistance, lower resistance creates higher RPM (less load on the engine), higher RPM at a given throttle setting means greater efficiency and better performance and MPG.

Generally. YMMV

You can get cupped edges on aluminum props. Whether it provides lift or not depends on where the cupping is applied. See this link for a good summary:

https://ptprop.com/index.php?option=com_content&task=view&id=43&Itemid=62

Not all SS props are cupped. Who ever told you that they were needs to go back to school.

Just to add, when I had my alum prop my boat topped out at 40.5 MPH on my best run, 1 day with the new SS prop I hit 41 MPH on my best run. Maybe the wind was blowing stronger or the tide was ripping that day but to gain a 1/2 MPH isn't even worth noting IMO.

I'm not saying I'd never grab a SS prop again but it wouldn't be for any extra speed.

These runs were of course trimmed up to the max with a light loads.

The really nice part about stainless is the ability to adjust pitch up or down . so if you find a prop that's used it can be pitched to hit your sweet spot in rpms. where I fish , in the marshes of sw Louisiana . stainless is the norm cause alum wears and is a lot softer , easier to bend or break . As far a wearing out lower unit cause its to heavy ,I don't know about that, there are some old outboards out here that's been running for 20 or 30 years with out many problems if properly maintained and most run stainless. Down here we can fish dang near all year and then there is hunting in amongst there as well , so some of us put quite a few hrs on an outboard in some nasty conditions ... imo stainless is the way to go