Yamaha prop cracked
 

Our other boat is a 30ft rigid inflatable with twin Yamaha diesel sterndrives, or Hydradrives as they are called.

I have yet to take it for a run, but it allegedly does 55mph. I don't know what the gear ratio is but I do know that the diesels only spin to about 3900 rpm.

One of the props has a crack as if a blade is about to let go.

We have sent it out to be welded but I have been told the metal is quite brittle and it may shatter when they weld it. Has anyone heard of this before.

It is a 3 blade 21 pitch prop but the diameter is quite large, guessing just over 16 inches. I was wondering what else I can put on it. The spline looks like Mercury.

Is there any truth to a 1 inch reduction in diameter is worth about 1.5 increase in pitch?