Switching from Alu to SS Prop - change in pitch required ??

Canufixit2

Petty Officer 3rd Class
Joined
May 20, 2016
Messages
99
Hi, There is SOOoooo much stuff on this issue, and I've sifted through plenty..... Thought I'd just ask a specific question.

Going from a acceptable Alu Prop to SS......

Rig;
2000 Suntracker 18' party barge.
2018 Merc 4Stroke Command thrust 60 hp.
Current prop - Merc Black Diamond 14" x 11p rh Aluminum.
MAx rpm 5800 approx 20 mph. (This old Pontoon is Heavy!)

Just bought a Merc Vengeance Stainless steel 14 "x 10" Pitch prop.

So ... Dropping 1" pitch and changing to Stainless.

Did I just screw up ??

Thanks! (Please be nice?)
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
To be honest, any time one swaps between AL and SS, it really is a Crapshoot, an Apples to Oranges comparison. They are so many different props, and each brand. and model has its own charateristics.
You have introduced a few variables, Different Material, while both are Mercury Props, they are not identical, differences in Diameter, blade area, blade shape, cup and rake.
The only way to find out is to run it. It might be Great, Good, Fair, No Different, or Outright Lousy.

What is the WOT rpm range for your engine?
 
Last edited:

porscheguy

Chief Petty Officer
Joined
Jan 17, 2013
Messages
441
You’ll probably be just fine and you may even pick up a few rpm. The vengeance is not an aggressive performance prop. It’s really a stainless casting of the standard aluminum black diamond.

but as with all props, you won’t really know until you test it.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Hi, There is SOOoooo much stuff on this issue, and I've sifted through plenty..... Thought I'd just ask a specific question.

Going from a acceptable Alu Prop to SS......

Rig;
2000 Suntracker 18' party barge.
2018 Merc 4Stroke Command thrust 60 hp.
Current prop - Merc Black Diamond 14" x 11p rh Aluminum.
MAx rpm 5800 approx 20 mph. (This old Pontoon is Heavy!)

Just bought a Merc Vengeance Stainless steel 14 "x 10" Pitch prop.

So ... Dropping 1" pitch and changing to Stainless.

Did I just screw up ??

Thanks! (Please be nice?)

I don't think so. The SS performance enhancements will make up the 1" pitch you lost and probably give you some performance to boot. It'll eat into those too high rpms and spit out some mph. Wink!
 

wahlejim

Master Chief Petty Officer
Joined
Jul 23, 2015
Messages
884
Let's face it, how often are you going WOT on that pontoon? The lower pitch will help with acceleration and turning that beast, also may allow you to better tow something behind that beast. I think you will be quite happy with it, especially if that boat is fully loaded.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Always keen to hear how things like this end up. Only way is to try it. I doubt you will see any real significant gains really. The vengeance time after time usually fails to out perform the black max standard ally 3 blade of same pitch. It’s just a shiny and heavier version of it. It will look better though.
That 14” diameter might help a little though. Didn’t know they were that big in that pitch of prop for that engine.
I had great results from the enertia and tempest props for the CT engine. All be it on a 115 and on a fairly quick hull. Currently have a 19” enertia on it. It’s on the limiter at just about 6100/6150 rpm though and 43 mph gps. Going up one inch to a 20” enertia to try and get it spot on.
 
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