# Alum to SS



## crappiedude (Mar 12, 2006)

Okay so we already have a few prop threads going to try to figure out new sizes and performance. My question is a bit different.

I repowered to a Merc 60hp 4 stroke last year. I had them put on an alum prop at the dealer and they added a 10.5x13.0 Black Max and it seems to be just about perfect. Max RPM's for motor is 5500-6000 and at wot with the motor trimmed up it runs just at 6000-6100 rpm. Under normal everyday use I run around 5000 to get around. Seems to get good performance and economy right here so I'm happy with it.
My question is, what will happen if I just switch to a ss prop of the same exact size.
I was under the impression that the only thing that would change is you may be a little better speed since the ss won't flex under load like an aluminum.


----------



## backfar (Sep 24, 2014)

From my own experience switching to a ss prop will get you out of the hole faster and better top speed....hole shot is better because it dont flex as much as aluminum.... top speed will increase because most ss props have a slightly larger cup...that allows for more trim...more trim it will lift boat outa water more.....this was my experience with a 19ft fourwinns with a v6....gained 5mph


----------



## Insco (Apr 9, 2008)

I posted in a recent thread. I went from a 14x17 aluminum to a 13.75 x 17 stainless and my boat bogged on both low end and top speed. i switched to a 13.75x15 and gained some holeshot but no top end speed. I now run about 5800rpm at wot. The aluminum ran about 5500rpm.


----------



## SemperFi (Mar 10, 2014)

The SS doesn't flex like the aluminum prop will which will give you more bite in the water.. but a downfall to the SS prop is that if you hit something in the water like a floating log. The aluminum prop will bend or break and the SS prop will stay strong and possibly mess up your shaft. Cost much more in repairs!


----------



## backfar (Sep 24, 2014)

Props are still somewhat of a mystery??? When i bought my fourwinns back in 89 we tried 8 different props.....different manufacturers and different sizes... all the props being 3 blade and between 17 and 19 pitch....what i can tell you without a doubt they ALL performed differently... maybe try to find a marina that will loan you a few to get it dialed in?


----------



## crappiedude (Mar 12, 2006)

SemperFi said:


> a downfall to the SS prop is that if you hit something in the water like a floating log.


according to what I've seen on a few Mercury YouTubes the new style hubs will help protect the outboard from damage because the hub is designed to fail in the event of a major impact.


----------



## capt j-rod (Feb 14, 2008)

hub should give you protection. More blades will give you a better hole shot and carry the loads better at low and mid range. You will suffer on the top end a little bit. A cupped prop will give better performance, but everything has a cost. I have never run WOT for an extended time and it rarely is an option on Erie. I focus my attention to the low end performance as well as mid range cruise. My 150 Yamaha spends most of its life between 3500-4500. It is also very important that I can maintain plane at 15mph for rough water. Props are like having a four speed manual transmission but you can only pick one gear. Decide what you need the most out of your rig and prop it accordingly. I could redline my motor very easily due to the pitch, but as I stated, I don't need top end. FWIW I can easily run 40+ mph on my high end and I cruise in the thirties with ease. That is plenty of speed for a 20' Lund and my application.


----------



## Popspastime (Apr 1, 2014)

From what I'm told so far from Prop MD the aluminum has a lot more slip at the top where a SS doesn't and there for you may lose some RPM's due to that. Almost all props are cupped and very few with an exception to Inboard wheels that might come straight bladed. I should have my 3rd prop tomorrow, 3 blade SS (same Dia. and pitch) as the 4 blade and there saying I should scrub 300 - 400 of of WOT witch should bring it in at 5700 to 5800 I'm hoping


----------



## crappiedude (Mar 12, 2006)

FWIW at wot I run 6000-6100 rpm & 33/34 mph normally I'll back down to about 4800-5000 rpm and run around 26-28 mph.
Because the lake I usually fish has a lot of flooded timber I'd like the durability of a ss prop. If you spend any time back in the covers you will hit something. I've damaged an aluminum prop a time or two on the old motor so that's why I'm thinking ss.

So what I think I'm hearing is that going from the aluminum to the exact same size ss I will probably see a little drop in the rpms because the alum prop was slipping AND I could also see a little increase in hole shot and maybe top end speed because the ss has a better bite.
I'm still just in the thinking stage so who knows what I'll do.


----------



## sherman51 (Apr 12, 2011)

another good thing about ss is if you hit a limb it will bend instead of cracking or breaking like with alum. if you damage an alum prop you need to have it rebuilt. with a ss prop if it is just bent on the edge you can take a 2x4 for backing and use a small hammer and beat it back in shape.
sherman


----------



## Popspastime (Apr 1, 2014)

crappiedude,
I spoke with Michigan wheel for a long while on this subject and told them what I had, motor,prop, and my goal. THEY are the ones who told me the size and type I'd need in SS altho I was not able to purchase from them they sent me to a prop dealer with part numbers. The dealer who also are experts totally agreed with the parts and sizing Michigan Wheel recommended. So that's where I am right now with my whole deal. Don't compare stories with others with larger motors because its all different, smaller motors are tougher to dial in without significant changes.


----------



## fastwater (Apr 1, 2014)

Popspastime said:


> crappiedude,
> I spoke with Michigan wheel for a long while on this subject and told them what I had, motor,prop, and my goal. THEY are the ones who told me the size and type I'd need in SS altho I was not able to purchase from them they sent me to a prop dealer with part numbers. The dealer who also are experts totally agreed with the parts and sizing Michigan Wheel recommended. So that's where I am right now with my whole deal. Don't compare stories with others with larger motors because its all different, smaller motors are tougher to dial in without significant changes.


Absolutely on comparing like size mtrs...
...and like size boats.

When comparing RPM's, hole shots, top end, and RPM's of even like sized mtrs, the boat itself has to be considered also. My 50hp on a v bottom that weighs 1200lb won't act the as your 50hp on a flat John boat that weighs 800lb


----------



## Popspastime (Apr 1, 2014)

crappiedude, .. here's the update. 
Recap.. started with the factory prop, 10.6 x 12 Four Blade turning 6200 WOT (too much) Decided I needed another blade and also upgrade in efficiency and kill a few rpm's with 5700 to 5800 Wot targeted and go Stainless. The supplier suggested to do that step up 2 inches on the pitch 10.5 x 14 Three Blade SS and that should equal 400+ rpm's landing me right in the general area. Installed it and tested, 4500 RPM's WOT and killed everything (wrong prop) Bit way to good. 
Called Mich Wheel and spoke extensively and they suggested to go the same Diam and Pitch but in a 3 blade 10.6 x 12 SS but I had to contact a dealer with my part numbers to purchase from them (understood). Received prop today, installed and headed for the lake certain this is the one. Warmed up the motor (40 HP Merc 4 Stroke) and worked the throttle slowly up. All thru and up to 4500 rpms it was smooth and I increased my speed by 3.5 mph at 4500. From 4500 to 5000 she went right to 30 (where it was top speed before) mph with more throttle to go.Increased the throttle and 5200 was all it was going to do trimmed up all the way, so I lost 1000 rpm's using the same Dia and pitch with the 3 Blade SS. 
Sooo Hole-shot was good to great, mid range picked up speed thru efficiency, previous top end speed was met at less RPM's, WOT is still short 600 Rpm's. (Prop going back)
Tech is sending another manufacture in the same configuration and is certain it will be in the groove. 
Moral to the story "All Props Are NOT Created Equal"
More to follow.


----------



## crappiedude (Mar 12, 2006)

Pops....That seems crazy. So these guys let you try a prop before you buy it?


----------



## Popspastime (Apr 1, 2014)

crappiedude said:


> Pops....That seems crazy. So these guys let you try a prop before you buy it?


Yes, this market is so "Not by the book" why would you spend that much for something they recommend that doesn't work if there was no return? You'll see when you try to get one for yours, I'm just trying to save you some steps and also prove that there are NO actual given numbers on these things as far as adjustment.


----------



## duxsrus (Mar 3, 2011)

Crappiedude, call Delta Propellers over in Cleves 513-467-0601. The owner can tell you exactly what you need. Last time I bought a prop on his recommendation, it was exactly what I was looking for, however he said if it wasn't right after testing it out, bring it back and he'd swap it out for me.


----------



## crappiedude (Mar 12, 2006)

duxsrus said:


> call Delta Propellers over in Cleves 513-467-0601.


Thanks, I forgot about these guys.


----------



## Popspastime (Apr 1, 2014)

Sent the last Mich wheel back and received a Pro Tech 3 Blade Cleaver style SS prop made in LA. The prop is the same size as the 4 blade original to the motor, 10.5 x 12. Ran the boat yesterday at all speeds. Speeds are all GPS and RPM's are off the tach. The boat was fully loaded but only I was in it (no passenger). Eased it away from the dock until the motor was warmed up and took it to 4000 rpm and held it. The boat lifted nicely, planed right off, and I trimmed it out. Gps speed was 26 mph, that's 2.5 Mph faster then the factory prop. Took it to 5000 and the speed went to 29.5 mph and the motor was purring. ( That was the original speed at 6200 RPM's) With doubtful hesitation I eased the throttle for more. The engine wound out to 5800 Rpm's (BINGO) and trimmed the motor even taller. The GPS speed was 33.9 Mph ..WOW. The prop kept the stern lifted and the bow planted without porpoising like it did before at a high trim and speed. 
Gained efficiency and speed at the cruising speed I run it (4000 - 4200). Still jumps out of the hole and runs almost 4 mph faster at WOT. This was the 5th prop tried to get this thing dialed in so make sure if you purchase ANY prop you can return it. I found out these props are NOT by the book and are NOT created equal.


----------



## firemanmike2127 (Mar 17, 2013)

Good to hear that you found a prop that was very well suited to your application. Just curious....what type & length of fishing boat are you running. Is it a tiller steer or equipped with a side console ? Also, how about the time to plane with a heavy load ? Just wondered if the factory aluminum 4 blade was significantly better with regards to just the holeshot. Mike


----------



## Popspastime (Apr 1, 2014)

It's a 16.5 Lund side console. Gets up and out just as fast now with the 3 blade as it did with the 4. At it's heaviest I'd probably add 1 more person, that's it. (another 200 lbs.) Setting mid-ship it shouldn't affect much other then maybe the top end a skoatch.. It will flop out on plane at slower speeds as well and stay there.


----------



## crappiedude (Mar 12, 2006)

So if I'm reading this right...going from an alum to SS prop of the same size you increased speed and decreased max RPM. This was the results I was told I would get if I changed props.


----------



## MassillonBuckeye (May 3, 2010)

I dont think a 60HP motor is causing much "flex" in a prop compared to say a 250 or 300 so I'm guessing there won't be much of a difference at all. Pitch is going to have much more effect on performance.


----------



## Popspastime (Apr 1, 2014)

crappiedude said:


> So if I'm reading this right...going from an alum to SS prop of the same size you increased speed and decreased max RPM. This was the results I was told I would get if I changed props.


In short yes.. but. Some props have more blade area then others called "RAKE" and each blade can grab more water then say a Cleaver type configuration (shorter blade) which is on the motor right now making me grin ear to ear. And with more rake (longer blade) on the blade it can really kill your RPM's like it did mine. In theory it's supposed to work like you were told but in reality it doesn't work just as easy as buying the same size wheel in Stainless and your done, doesn't happen. "Lesson Learned" 
Also MB.. there's a lot of flex and slip in any aluminum prop, from 10 hp to 300 hp.


----------



## MassillonBuckeye (May 3, 2010)

Popspastime said:


> In short yes.. but. Some props have more blade area then others called "RAKE" and each blade can grab more water then say a Cleaver type configuration (shorter blade) which is on the motor right now making me grin ear to ear. And with more rake (longer blade) on the blade it can really kill your RPM's like it did mine. In theory it's supposed to work like you were told but in reality it doesn't work just as easy as buying the same size wheel in Stainless and your done, doesn't happen. "Lesson Learned"
> Also MB.. there's a lot of flex and slip in any aluminum prop, from 10 hp to 300 hp.


Slip sure. Flex? I disagree. They just aren't torquey enough in my opinion. And it's only going to flex on a hard hole shot anyhow. I'd like to see some documentation. I don't think its enough to worry about with the cost difference.
Here's a discussion on the topic between folks a lot smarter than I.

"Re: Prop flex...how much and when

Smart, Spike and chuck are both right in their postulations on aluminum props. The biggest differences in aluminum and SS props has to do with blade geometry as under 45 MPH aluminum props do not show enough deformation to account for any change in pitch because of blade flex. IF you are planning on running your boat over 65 MPH then you might want to start considering blade flex.
But if you are not going to be doing that then you need to decide what particular blade geometry is best for your hull form, HP and intended uses, that is MUcH more Important."

http://forums.iboats.com/forum/gene...and-topics/360962-prop-flex-how-much-and-when

Here's another informative discussion that basically says the same thing.
https://www.microskiff.com/threads/aluminum-prop-flex-vs-stainless-prop-prop-geek-special.30010/

As you were


----------



## Popspastime (Apr 1, 2014)

Next time we need to make the right selection we'll contact you.


----------



## crappiedude (Mar 12, 2006)

Popspastime said:


> In theory it's supposed to work like you were told but in reality it doesn't work just as easy as buying the same size wheel in Stainless and your done, doesn't happen. "Lesson Learned"


I was afraid it wouldn't be that easy... My buddy has a 50 HP merc 4 stroke. I think I'm going to try to see what size his it. It looks to be very similar to my but we need to pull it to verify the size. I'm hoping I can use it as a starting point.
Thanks for the input Pops


----------



## Popspastime (Apr 1, 2014)

I would suggest going right to Pro Tech and get theirs in the cleaver style just like the one I got for mine. Call "Ben" at Prop MD and he'll get you set up, he knows his stuff on props. A dollar to a doughnut he chuckles and sets you up with the Pro Tech.. lol.
I've been running mine the last 4 days and I love it.


----------



## MassillonBuckeye (May 3, 2010)

Popspastime said:


> Next time we need to make the right selection we'll contact you.


He kinda did when he posted on a public forum.  Glad I could be of assistance! No need to be rude.


----------

