Stainless Steel vs. Aluminum Propeller

[greg82255]

Hello,

So I have a 19' checkmate with a Mercruiser 305 engine with 198 HP. I am about to finish some modifications to the engine that, according to manuals I have read and dealers I have talked to, will put it at about 230-240 horsepower, and I am looking to change the propeller from aluminum to stainless. I currently have a 14.25 x 21" mercury aluminum prop on there right now, and I get about 52 mph out of it at 4300 rpm (before I modified the engine). Ive heard that a stainless steel prop will increase performance by about 3 mph and increase fuel economy. I have also heard that when you make the switch from aluminum to stainless, you have to change the pitch. So my question is, what size/pitch prop should I use for a 230-240 horsepower engine if top speed (maybe even break 60mph?) and acceleration is what I want to accomplish? Any help would be greatly appreciated.

 

[robjen1019]

Re: Stainless Steel vs. Aluminum Propeller

I would run it with the old prop first to see what your real world numbers are before you start buying props. Once you find your wot with the old prop you can figure out the rest.

 

[Bondo]

Re: Stainless Steel vs. Aluminum Propeller

Ayuh,... This is the I/O forum,... Prop forum is farther up the main page....

But anyways,...
You're only turning 4300 rpms now,...
Do whatever you're doing to the motor,+ Try it....
You're gonna need to see 4900/ 5000rpms to reach those hp #s....

Armed with that information,... Post your prop questions up in the prop forum....

 

[Godfirst]

Re: Stainless Steel vs. Aluminum Propeller

Hi there is many info on past posts on this perspective just make sure if you go stainless don't hit anything a lower drive unit can be very expensive

 

[sr280da]

Re: Stainless Steel vs. Aluminum Propeller

If you can get by with Alu, stay that way. Adding SS props unless you are on a trailer and hardly use your boat is an invitation to galvanic corrosion on any part of the I/O that is immersed in water.

I have twin SS props on my BIII and every year is spent cleaning and re-painting the aluminum to keep it from disappearing. Also you might want to consider upgrading the Mercathode as well if you add the SS prop.

 

[carrera1984]

Re: Stainless Steel vs. Aluminum Propeller

Hi there is many info on past posts on this perspective just make sure if you go stainless don't hit anything a lower drive unit can be very expensive

I can tell you all about that... This is actually why im switching to aluminum blade...

 

[ArcadianStar]

Re: Stainless Steel vs. Aluminum Propeller

I had a 27' Rayson Craft with a 502 Merc Bravo, I ran a stainless propeller on that boat the entire time I owned it. I once saw a bouy in the middle of the river, at Willow Valley, and drove over to see what the sign on the bouy said. It said, "Shallow water. I hit bottom BIG TIME. All I broke was a 15 dollar plastic Flo Torque hub driver.

All modern props, I think, use the same hub kit with ALUMINUM and Stainless. The difference, you slam into a rock bar like I did with an aluminum prop, you will ruin your aluminum prop and your hub kit. With a stainless prop, you only ruin the hub kit.

I never suggest repairing a stainless prop until you can feel it viberate.

The Flo Torque hub kit is designed to take a hit and not damage the drive, aluminum or stainless...it doesn't know the difference....and I feel it works very well!

ADD:

Flo Torque kit say up to 400 HP, but my boat had more than that for the four summers I owed it and it never SPUN a hub expect when I read the sign...

LAST ADD:

I've seen guys go through four aluminums in a season and a guy on the same river with a stainless goes through NONE!!!!

 

[Snobike Mike]

Re: Stainless Steel vs. Aluminum Propeller

If you can get by with Alu, stay that way. Adding SS props unless you are on a trailer and hardly use your boat is an invitation to galvanic corrosion on any part of the I/O that is immersed in water.

I have twin SS props on my BIII and every year is spent cleaning and re-painting the aluminum to keep it from disappearing. Also you might want to consider upgrading the Mercathode as well if you add the SS prop.

Your problem is not SS props. You either have no anodes r the wrong anodes or you are sitting in water with a rogue electrical current. There is no way your drive should require repainting as you describe every year (the only other issue could be a very poor paint job every year I guess).

 

[bruceb58]

Re: Stainless Steel vs. Aluminum Propeller

I never suggest repairing a stainless prop until you can feel it viberate.

I disagree. Just because you can't feel it doesn't mean your bearings in your drive can't. Any damage to my prop and it gets repaired and rebalanced.

As far as RPM with a stainless prop is concerned, everything being equal, you will pick up some RPMs with indentiacl pitch. The reason is that the stainless blades are thinner and there is some less drag.

If you happen to have a knack of hitting your props, stick with aluminum. Way more forgiving on your drive.

 

[bruceb58]

Re: Stainless Steel vs. Aluminum Propeller

Your problem is not SS props. You either have no anodes r the wrong anodes or you are sitting in water with a rogue electrical current. There is no way your drive should require repainting as you describe every year (the only other issue could be a very poor paint job every year I guess).

This is a known problem with Bravo 3 drives.

 

[Snobike Mike]

Re: Stainless Steel vs. Aluminum Propeller

This is a known problem with Bravo 3 drives.

Well, kinda.

They did have corrosion problems up to the early 2000's but of course that doesn't mean that every B3 had this problem and certainly not to the extent that this poster indicated requiring a yearly repaint of the drive. There has to be some other extenuating circumstances in that specific example.

Somewhere around 03-05 they resolved the problem with more/diffferent anodes and a few other changes.

My primary point is that SS props don't mean you are driveless due to corrosion within a year.

I like my SS props just fine.

Cheers.

 

[sr280da]

Re: Stainless Steel vs. Aluminum Propeller

Zincs are replaced annually, mercathode is tested and functioning properly. Boat is on a mooring in a small cove with no possibility of stray current.

Stainless steel immersed in water next to aluminum equals galvanic corrosion. It is just basic chemistry. Zincs and things like mecathodes will slow it down, but not stop it. So adding a big lump of stainless onto an aluminum sterndrive is a step back if the same propulsion can be achieved with an aluminum prop.

As an FYI, Bravo III props do not have hubs. Whatever the prop hits is transmitted directly to the drive and gearing.

 

[themaniam1]

Re: Stainless Steel vs. Aluminum Propeller

I know you can get aluminum props for the Alphas but I thought there was no choice with the B3. There is only SS for B3 right?