Switch to stainless on new project

[DVW]

Need prop recommendation for my 22SXL project. The boat description can be found in the Do-It-Yourself section of this forum. During development of the boat I went thru 4 different aluminum propellers. Now that the project is more or less done I want to switch to a stainless prop for a little more speed. I now have Mercury Nemesis 4 blade aluminum prop 12.5” dia X 19” pitch with Yamaha F115 power. The current top speed is 50 mph at 6200 rpm (std 2.15:1 lower unit). As you can see from the attach photo the so called cavitation plate is slightly exposed at speed. Despite this as I trim the motor up to achieve top speed that speed is limited by porpoising not aeration. Any help would be appreciated.

 

[Michiman]

It’s my understanding that the rule of thumb is that a SS prop is not appropriate under 150 HP where prop flex is less of a problem.

 

[Bill N]

At 50 mph with two 115's, any further gain will be extremely incremental.
But what do I know? I would have said not to expect over 45. You've definitely exceeded my expectations already!

 

[DVW]

At 50 mph with two 115's, any further gain will be extremely incremental.
But what do I know? I would have said not to expect over 45. You've definitely exceeded my expectations already!

I expect a speed improvement because my props are all wrong. Typical of most 4-blade props my props where designed for thrust not speed. I bought them because they where cheap and my dealer gave me a generous return policy. I still will need that unless I nail it the first time.