Stainless prop's wrecking lower units

[Andrew Leigh]

Hi,

Life is filled with so much misinformation and I don't believe the following one.

If you use a stainless prop and you hit a submerged item you will wreck your lower unit. I always thought that there was a shear device in the hub of the prop? The theory being that the alloy prop will break before the lower unit breaks?

Bought a new boat recently and it has as a spare a 19" spare stainless prop while the 19" aluminium prop remains fitted?


Cheers
Andrew

 

[Barnacle_Bill]

Re: Stainless prop's wrecking lower units

Not true. The hub in the prop is designed to give first. Along with some bent or destroyed blades.

 

[Bondo]

Re: Stainless prop's wrecking lower units

Ayuh,..........

That's the Design Theory anyways.......

I've seen a Quite a Few Trashed outdrives with both Aluminum,+ SSteel props involved.......

 

[Andrew Leigh]

Re: Stainless prop's wrecking lower units

Thanks,

any reason I should not fit the stainless? In fact not being that familiar with prop theory any reason for keeping the aluminium on?

Cheers
Andrew

 

[DJ]

Re: Stainless prop's wrecking lower units

Put the SS one on as long as it is the right diameter and pitch.

SS props do not flex as much as AL ones do so the pitch may be a bit different. Watch your tachometer.

 

[Frank Acampora]

Re: Stainless prop's wrecking lower units

Well, thats like saying that stronger fenders on a car are bad because in a crash they cause more property damage. The fact is that props are not meant to physically impact underwater objects. No matter what you hit, if you hit it hard enough, any prop may cause gearcase damage.

 

[Andrew Leigh]

Re: Stainless prop's wrecking lower units

Hi

Thanks.

Will not be able to take the boat out again until early January. We are leaving for the Kruger National Park on Saturday, three weeks of glorious camping in the 40?C plus heat of Africa. Can't wait for all the Lions, Elephants, Leopards etc. Ice cold beers with 400g steaks and the call of the wild as your sound track.

Stainless will go back on, and yes unlike some of my countrymen I choose safe routes on the water and will always consult the locals in unchartered waters. I do suppose hpowever that you can't always get it right.


Cheers
Andrew

 

[Frank Acampora]

Re: Stainless prop's wrecking lower units

Well, you know the old saying: "If you ain't run aground, you ain't been around!" Just say an invocation over those steaks and splash a little beer into the water to appease Neptune and ask for a safe passage.

 

[Texasmark]

Re: Stainless prop's wrecking lower units

The damage occurs when the impact is transmitted to the lower unit before the prop has had time to react and that's any prop material with any hub......kinda like a sparkplug. Today's ignition systems have a real steep rise time and the idea is to smack the plug and fire it before the voltage has had time to bleed off through insulator contamination.

The only time I would use an alum prop is if I boated where rocks were known to exist unexpectedly in navigatible waters; not referring to deliberately placed rip rap sort of stuff like protecting a dam or a breakwater. Lake Austin in Texas (Named after, and adjacent to, Austin, TX.) is just such a place.

For everything else, I don't like a dinged up prop and SS just looks pretty longer, besides all the other benefits.

My 2c,

Mark

 

[whywhyzed]

Re: Stainless prop's wrecking lower units

On electric shift OMC's, the heavy SS props have been known to break the tangs off the clutch springs during directional shifts, especially if the engine rpm's are too high, or during dock avoidance maneuvers

 

[AGENT 37]

Re: Stainless prop's wrecking lower units

I always run an aluminum prop for a number of reasons. Aluminum is cheaper to replace, you could sell you SS prop for instance and buy two or three spare aluminum props. I believe that a light weight aluminum prop is easier as far as normal wear and tear goes on with the gears; especially in high frequency shift applications. We have a 225 in the shop that we can't get apart because it has the drive shaft splines worn together from low speed clutching in and out of gear because the motor would push the boat to fast for trolling at idle in gear. It had a big heavy stainless prop on it. Just a theory, but if you hold a SS prop in one hand and an aluminum in the other you can see the difference. We all know that it takes more energy to get a heavier object set into motion as well as arrest that motion and all of that energy has to be transfered through unions and gears. Your average user is not going to face the problem that our 225 had however. And the third reason that I use aluminum is to help counteract the corrosion that goes on in the water. Aluminum is a softer metal than steel and knowing how corrosion works I would not want a big chunk of steel down in the water attached to the leg on my mostly aluminum outboard on an all aluminum boat. Look a the sacrificial zinc anodes and you can see how softer metals take the brunt of the blow. Aluminum does the same thing when paired up with steel or any other stronger metal that the zinc does when paired up with aluminum. Uniform corrosion that happens with similar metals is less exaggerated than the localized corrosion which can devastate small areas in a very short time. You can see it as simply as looking at the condition of the zincs on an outboard mounted to a fiberglass boat and looking at the same mounted to an aluminum boat that it not coated. You have to change out the zincs on the fiberglass more frequently because all of the electrolysis is focused on the outboard and not spread out over the entire hull of the boat. Just my way of looking at things. I think that stainless props are sharp looking and definitely hold up to the little dings better though.

 

[drewmitch44]

Re: Stainless prop's wrecking lower units

I hear ya about the weight thing on the 2 different props as far as it taking more energy to spin the heavier one but.... Sience tells us that an object that is heavier when set into motion has more energy. I know that the aluminum prop is heavier but if you were the oupboard you would not be able to tell a difference. To me its all a matter of preference. I use aluminum props but not because i dont like SS ones its just that i cant afford SS props. I think the SS props are much better and will make no difference to your motor or lower unit. Matter of fact lots of people think that SS props are much easier on the components. Thats just my 2 cents. What do i know though.

 

[oops!]

Re: Stainless prop's wrecking lower units

im faced with this delema also.
i boat in lakes.
i am soooo careful of the prop. however every time i pull the boat out the prop has another ding!!!!
cant beleive it!
last alum i had, the zinc came undone and droped in the way of the prop at 4000 rpm. i couldnt figger out what the vibration was from! took me a full two mins of scratchin my head!

problem is now im goin b1/ss. and im afraid of a 500 bill every time i go boating or a drive

more input please

 

[flabum]

Re: Stainless prop's wrecking lower units

A new boater is better off starting with an aluminum prop simply because he is more incined to bump into things. It is easier and cheaper to fix or replace an aluminum prop than a SS prop. I sAy as long as the aluminum prop keeps you in the WOT range you need, run it. then once you know the boat and where you run it, switch to the SS.

 

[ron7000]

Re: Stainless prop's wrecking lower units

The damage occurs when the impact is transmitted to the lower unit before the prop has had time to react and that's any prop material with any hub......kinda like a sparkplug. Today's ignition systems have a real steep rise time and the idea is to smack the plug and fire it before the voltage has had time to bleed off through insulator contamination.

uh, what?

 

[Arima90]

Re: Stainless prop's wrecking lower units

We generally use the aluminum props for a few reasons: 1) a thief will gravitate towards the shiny stainless steel and they know what their worth 2) just like any drive system, make the weakest link the least expensive to repair (prop -vs.- lower unit?) 3) less expensive to try new size and pitch. There are opinions on both sides of the coin and I like those fancy SS props but those three reasons listed above will keep us with the aluminum.

 

[jimmbo]

Re: Stainless prop's wrecking lower units

I prefer to run stainless even after bending a propshaft. Neat thing about a stainless steel prop is that instead of the blades snapping off they just keep bending until the prop resenbles a ball.

 

[Texasmark]

Re: Stainless prop's wrecking lower units

Drew, You are talking about kinetic energy and the mass (weight) of the object in motion is a determining part of that energy. Heavier the object, more energy it possess under a given set of circumstances.

Problem is, with a prop, you have to also consider the resistance of the water that it is pushing against and if you consider the whole power loop, I think prop weight is not all that important.

Buttttttttt I will tell you this. If you have a Merc with a 3 cylinder engine, you notice the difference in that kinetic energy when at idle.....it's called "clutch dog rattle" and the heavier the prop, the more it rattles.

Mark

 

[tommays]

Re: Stainless prop's wrecking lower units

And SS prop is going to take a bigger hit before bending BUT your going to have to take a BIG hit on the skeg to even get to a rock


I like Alu props as there cheep and i dont have to worry about them walking

BUT i think and ALU could dammage gears also if you really jam it up with a ROCK or LOG at any kind of RPM




Tommays

 

[reelfishin]

Re: Stainless prop's wrecking lower units

I boat mostly in rivers and back bays, there's always plenty of hidden debris floating that you can't see. I've run both aluminum and stainless props, both have their benefits. Stainless will withstand more without damage, but when it does take a harder hit, I feel for one it does impart a larger impact on the rest of the drive line and they are harder or more expensive to repair.
An aluminum prop will dent and ding easier, it will even bend on a harder hit, but I like the ability to be able to weld and reshape it easily. I've gotten pretty good at eyeballing the pitch and shape and getting it back in shape. I have two stainless props that I use when running in sandy areas, the one I use most is worn so bad the edges of the blades are sharp, but it has no dents. An aluminum prop would already have been gone by now. If I left my boat in full time, and ran more open water, I'd probably opt for only a stainless prop, but since I trailer my boat, I've stayed with aluminum. I also like the ability cost wise to have several more spare props and that gives me the ability to change prop pitch for different occasions. I keep a lower pitch prop for heavier loads or for towing. Stainless props do also attract thieves, I've watched several disappear down at the docks. They seem to know when theres a shine new one down there. Of course, they normally don't just take the prop, usually the whole lower unit disappears too.