I'm kind of confused about SS prop pitch selection.

[StangLX302]

I've been doing a lot of reading on here and other forums about stainless props. Half of the info I've absorbed is that when choosing an SS prop, you should drop a pitch from whatever aluminum you were running because SS props do not flex and do not slip as much. Then, I've read that SS props have thinner blades and don't have as much drag as a comparably sized alum prop. By that logic, you would think RPM would go up.

So, by combining both things I've read. Both statements kind of cancel each other out and you should use the exact same pitch and size when switching to get the same WOT RPM.

Can someone with experience with this straighten me out here?

What I'm trying to figure out is that I'm running a 14.25 dia x 21 pitch Mercury Black Max aluminum prop. My WOT RPM is exactly 4800 RPM @ 43.9 MPH. This is exactly where this engine is supposed to run. I want to get an SS prop for more speed, but I don't want the WOT RPM to change at all.

 

[Frank Acampora]

Re: I'm kind of confused about SS prop pitch selection.

.At a given speed or rpm, stainless does not flex as much as aluminum so more horsepower goes into moving the boat, not turning the prop (simplistic explanation) Also, Stainless blades are generally thinner and travel through the water easier. Again, more horsepower goes into moving the boat. The two statements do not cancel--they re-inforce each other. Generally, the same pitch Stainless prop will turn 200-400 RPM faster than an aluminum prop and deliver 1-2 MPH more. Again, simplistic answer--it's really a little more complex than that and of course will vary from boat to boat.

 

[BAYLINER185]

Re: I'm kind of confused about SS prop pitch selection.

Ive been told once you figure out your prop pitch you pretty much keep the same exact size and pitch and you just go Stainless. That was my plan.

I have a 14 X 23 on my BAYLINER 185 and im hitting a top speed of 52 MPH at around 4800~5000RPM. If I decide to do the SS prop I was planning on getting one exactly the same as my aluminum.

My dealer said that as you mentioned there is less flex and slip w/ Stainless steel and in reality you get closer to the props rated pitch. For example Im running a 23" pitch so a stainless will get you a lot closer to 23" in one rotation then the aluminum does in one rotation. Its not a perfect 23" as you are turning in water and there is no 100% lock up but its better then the alum. prop.

My dealer also told me that on my BAYLINER I might not really be able to ever tell the difference between SS and Aluminum props because the performance is NOT night and day and it will be hard to see much change.

Other then the SS looking cool. So My thoughts are to keep the same pitch if your happy with your performance.


My dealer also told me that on my BAYLINER I may not really be able to ever tell the differance between SS and Aluminum props because the performance is NOT night and day and it will be hard to see much change.

Other then the SS looking cool. So My thoughts are to keep the same pitch if your happy with your performance.

 

[StangLX302]

Re: I'm kind of confused about SS prop pitch selection.

.At a given speed or rpm, stainless does not flex as much as aluminum so more horsepower goes into moving the boat, not turning the prop (simplistic explanation) Also, Stainless blades are generally thinner and travel through the water easier. Again, more horsepower goes into moving the boat. The two statements do not cancel--they re-inforce each other. Generally, the same pitch Stainless prop will turn 200-400 RPM faster than an aluminum prop and deliver 1-2 MPH more. Again, simplistic answer--it's really a little more complex than that and of course will vary from boat to boat.

So, are you saying that if I get an SS prop in the same size as my aluminum, my engine RPM will stay the same?

 

[Crownie2]

Re: I'm kind of confused about SS prop pitch selection.

In your case, I would say that you should stick with the same pitch.

On my last SS prop switch (21" to 21"), the RPM's went down slightly and my speeds at all RPM's were faster. I believe this is because the increased efficiency loads the engine better and pulls it down slightly.

I noticed that out of the hole the boat actually seemed slower and this makes sense in light of the above. I believe this and the need for somewhat higher RPM's than the original setup are why many actually drop in pitch when going SS.

So - is good acceleration very important to you, or is good cruising speed more important? Which would you like to improve with this swap?

Another thing an SS prop will also do is hold (not blow out) in the turns better.

Hope this helps!

Bob

 

[tommays]

Re: I'm kind of confused about SS prop pitch selection.

And then there is the wide difference in prop brands


With the best ALU prop being as good or better than a marginal SS prop



Tommays

 

[rondi]

Re: I'm kind of confused about SS prop pitch selection.

Stang - have you made a choice or narrowed it down yet?

Still not convinced that an Enertia would be worth the extra $$ for our little 3.0's yet. So many choices out there. I'm sure you can get something to fulfill your needs for $300 or less.

An Apollo may be all you need or the Stiletto Advantage looks pretty good.

Here's a test on some 3 Blades that Walleyehed completed to help you out.

http://forums.iboats.com/showthread.php?t=178446

 

[Crownie2]

Re: I'm kind of confused about SS prop pitch selection.

And then there is the wide difference in prop brands

With the best ALU prop being as good or better than a marginal SS prop

Tommays

So true - I was going to say that but didn't get to it.

 

[Crownie2]

Re: I'm kind of confused about SS prop pitch selection.

Still not convinced that an Enertia would be worth the extra $$ for our little 3.0's yet. So many choices out there. I'm sure you can get something to fulfill your needs for $300 or less.

I believe you may right about this - I haven't seen anything testwise with this engine...

Bob

 

[StangLX302]

Re: I'm kind of confused about SS prop pitch selection.

Stang - have you made a choice or narrowed it down yet?

Still not convinced that an Enertia would be worth the extra $$ for our little 3.0's yet. So many choices out there. I'm sure you can get something to fulfill your needs for $300 or less.

An Apollo may be all you need or the Stiletto Advantage looks pretty good.

Here's a test on some 3 Blades that Walleyehed completed to help you out.

http://forums.iboats.com/showthread.php?t=178446

I'm 99% sure it's going to be a Stilletto. I've read that the Apollo props are made in China and are of poor quality and very inconsistant. The only bad thing about the Stilletto is that you have to buy a couple of things to make it fit because it's designed for non flo-torque II hub'd outdrives.

Also, I just called Stilletto and he recommended a 14.25 x 21" Advantage II. He also said if that it's not right, I can exchange for $40.00.

What do you guys think? I might order this thing tonight, so I'd like a few second opinions.

 

[rondi]

Re: I'm kind of confused about SS prop pitch selection.

So true - I was going to say that but didn't get to it.

Would that be a Hustler? . . . . is there any other HP aluminum's out there?

 

[rondi]

Re: I'm kind of confused about SS prop pitch selection.

I'm 99% sure it's going to be a Stilletto.

$99 on Ebay for a 21P - 15 spline - RH rotation - Advantage II. Needs no extra parts for our Alpha drives.
Don't waste another minute - use the Buy it now.

http://cgi.ebay.com/ebaymotors/STIL...ryZ26456QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[StangLX302]

Re: I'm kind of confused about SS prop pitch selection.

$99 on Ebay for a 21P - 15 spline - RH rotation - Advantage II. Needs no extra parts for our Alpha drives.
Don't waste another minute - use the Buy it now.

http://cgi.ebay.com/ebaymotors/STIL...ryZ26456QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Uggghhhhhh.......Probably right after you posted that, I signed off and haven't been on for 2 days.

Anyways, I found my perfect prop and I'm extremely impressed and finally satisfied. I installed a 13.75" x 21 pitch Quicksilver Silverado which is just a re-boxed Mercury Vegeance from what I understand. I took 'er out for a quick spin today and the water was VERY choppy. Even in the choppy water I went 45.6 GPS MPH. 43.9 was my absolute best with the Black Max and that was on glass like conditions. I'd guess it'd be good for even more speed without the chop. Mid range punch was a LOT more noticable as well. From 25-40 mph you can actually feel the acceleration now, instead of just waiting for the RPM to climb. Off a dead stop, plane times were quicker as well. I couldn't test for "blow out" in the turns because of the wave conditions. It was too choppy to try any crazy manuevers. I also noticed that it liked the trim higher than the aluminum when at WOT.

P.S. WOT RPM was right at 4800.

P.S.S. The "bling bling" factor on the trailer is cool as well.