Re: 1998 Johnson 200 Oceanrunner Que
You sir are headed in the wrong direction. You don't replace a SS with alum. Read the sales brochures and the reasons are spelled out there. The actual weight of the prop only comes into play when starting it revolving and not much then when compared to the weight of the water it's pushing.
Most OMC products run at 5500 tops, that I know, and you are close to the upper limit. You are getting about all you are going to get out of that boat. Did you do a GPS check on your speed or just using a regular pressure gauge?
We just got through working an Oceanrunner problem with another guy. If you will look up my responses and go back to a series entitled "motor position" as I recall you can see what this other guy had for a rig and what his numbers and problems were. Probably help you more than anything. Being an Oceanrunner, you are somewhat limited in your options......at least he was.
Mark