Differance between SS & aluminum.

[PatinIdaho]

Ok so boat is 24F Cuddy with a Bravo 1 and a 7.4L engine.
Came with 2 props.
One a 15 1/4X21P Aluminum mounted. Plane Aluminum has a cup
New 15 1/4X19P SS. Apollo XHS
Wondering if you know what the difference might be in use?.
Not had boat to lake yet so can't give any more numbers.
Just curious.

Oh forgot the aluminum prop also has A5 on it

 

[tpenfield]

Usually with Bravo & the power/torque of a 7.4, you go with stainless. You will have to determine if the 19P stainless is a good match for your boat and go from there. I have run aluminum with my previous boat (7.4 & B1) but it was only in a pinch and was not the greatest thing in the world.

 

[Texasmark]

Stainless for me on anything as long as you boat in relatively clear water. If you live in boulder country then alum and buy your props by the box.

 

[PatinIdaho]

So. Tried them both finally to day.
The 19P SS was not that good for my setup. 43ish MPH. Seems to make my boat porpus more no matter what trim i tried. Ok hole shot was nothing to brag about.
The 21P Aluminum was 50ish MPH same rpm as the SS. Seems to not porpus much at all once i get the right trim. About the same hole shot as the SS prop.
Think im going to stick with the aluminum prop but buy a new one the same brand and size. Quicksilver.

 

[Bonus Check]

So. Tried them both finally to day.
The 19P SS was not that good for my setup. 43ish MPH. Seems to make my boat porpus more no matter what trim i tried. Ok hole shot was nothing to brag about.
The 21P Aluminum was 50ish MPH same rpm as the SS. Seems to not porpus much at all once i get the right trim. About the same hole shot as the SS prop.
Think im going to stick with the aluminum prop but buy a new one the same brand and size. Quicksilver.

You want to get rid of your old ones? I might be interested. PM me if you are with a price.

 

[walleyehed]

So. Tried them both finally to day.
The 19P SS was not that good for my setup. 43ish MPH. Seems to make my boat porpus more no matter what trim i tried. Ok hole shot was nothing to brag about.
The 21P Aluminum was 50ish MPH same rpm as the SS. Seems to not porpus much at all once i get the right trim. About the same hole shot as the SS prop.
Think im going to stick with the aluminum prop but buy a new one the same brand and size. Quicksilver.

I hate to say this but the Apollo will disappoint you... A Mirage or Vengeance will provide better numbers for you. A Solas Rubex HR3 will provide good numbers as well.

 

[PatinIdaho]

Ok well now i feel kinda dumb.

So i wanted to pick up a new 21P prop and started looking at the prop numbers
QUICKSILVER 48 16318 A5 21P. It is 13-3/4X21P No longer available but has been changed to a Vengeance 13-3/4 X 21P SS prop
Turns out the one i thought was Aluminum is actually a SS prop also. I also assumed it was the same diameter but nope.
It is so dull i thought some one painted it silver to look like SS. Other then the finish it is in perfect shape. Just its weight should have been a clue....right.

http://forums.iboats.com/forum/engi...s-outdrives/54950-quicksilver-48-16318-a5-21p

So anyway now im wondering if there might be a little better fit as 13 3/4 seems kinda smallish for diameter for this size boat with a 7.4L engine?.


[h=1][/h]

 

[walleyehed]

Blade geometry has more to do with efficiency than diameter. It can have an effect on it but load dictates the requirement for diameter. The main reason you will see a trend to larger diameter when dropping to lower pitch. I'll talk to my Merc contact and see what he says.. give me a day or so..

 

[walleyehed]

Need to know which drive ratio you have... 1.3, 1.5, 1.6??
Looks like he's pushing torwards a Mirage...