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Hello!!
There are many options to consider in your case, depending on how efficient you want your rig to be, and how you plan to use the rig.
First, if you can get over the maximum RPM for the motor, you need to change props. Now, the basic jist of changing props is this: for every inch in pitch change, you will see an rpm change of about 100 to 150. In your case, (assuming 300 RPM average over), I would be looking at an increase of 1 inch up in pitch, and cupping added to the prop. This will do two things: lower your rpms, and also increase the prop's ability to "grab" the water, and force it back behind the boat better. It will help the boat turn, and it will also help for increased speed (in some cases)
In most cases with the smaller diameter hubs (like yours and mine) the larger pitch prop, the smaller the diameter. So...another calculation comes in, but is less significant. For every 1/4" change in diameter is roughly a 100 rpm change. So..if you go up in pitch, you may see a drop in diameter..which offsets in many cases. Your hole shot will reduce, but speed is increased along with a drop of some kind in RPM. If anything, move up in pitch, but not so much that you go 200 below the maximum rpm
Now...in terms of a steel prop...I used to run one on my Johnson 50 2 stroke. Worked fine, but went back to a squeeze cast aluminum. I try not to ding rocks when possible, and in the hp size you have, you will not notice a major difference in the boat.
Something to think about for a prop change is a Solas Alcup prop. (http://www.solas.com) This is the prop I settled on which allowed me to go to a larger pitch with cupping, and helped to keep rpms up to acceptable levels for me.
From here, you can do all sorts of things, like raising the motor on the transom to gain RPM etc., so...if that is something you want to consider, post it, and we'll go from there.
Steve
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