I have a 2014 Crownline 215ss with 350 mag and alpha 1 1.47 ratio the factory prop is a 19 pitch 3 blade aluminum and I’m wanting to go stainless steel and gain maybe a little more speed

I have a 2014 Crownline 215ss with 350 mag and alpha 1 1.47 ratio the factory prop is a 19 pitch 3 blade aluminum and I’m wanting to go stainless steel and gain maybe a little more speed

Need a little more information. What is the max rpm you are seeing with the current prop?

To be honest you are likely in the ideal range for prop pitch with that motor and outdrive ratio. You will notice some mild improvements with a 19" 3 blade stainless (Laser II or something similar) but don't expect earth shattering improvements.

For more mph you need more HP.

I'd go to a 17 4 blade aluminum and enjoy....did this on 2 of my buddy's boats...17 tahoe with a 3 liter and a 21 bayliner with a 5 liter. They were both pigs out of the hole and both had 3 blade stainless on them....went to a 4 blade aluminum and they are little rockets out of the hole and they both actually picked up some top end...1-2 mph. It's all about rotating mass and I would try/borrow a stainless from somewhere if you can before buying one. Honestly think you will be disappointed not to mention being an alpha, I would not put a stainless prop on an alpha ever. Shafts are too weak IMO and with the stainless you are exponentially raising the chances of bending or breaking a shaft if you hit something even as minor as heavy sand or a small log....that's just my opinion though.

Is go to a 19 stainless steel and call it a day. That already would seem dialed in to me for that motor and hull, you can try a 21 but I fear it's too much to turn

What are the details?

RPM with 19p alum?
GPS speed at max RPM?
Approx boat weight loaded at spec'd rpm/speed?

19" pitch is where you need to be. Get a Merc stainless 3 blade and call it good. You will not see any drastic performance gains by doing so. What I mean is that you aren't going to gain more than 1-2 mph, if that. I DO recommend switching to stainless in spite of that. Stronger blades, less blade flex etc yields more stable and consistent performance. Keep the old prop for a spare.

Are you sure that the factory prop was aluminum?? Never seen a Crownline that didn't have an SS prop.
If your WOT is under 4600rpms then go a 17" Mirage Plus. If its closer to 5000rpms then go with 19" Mirage Plus.