Suggest Ask Max-Prop
The prop listed under "The Boats", and in "Boat Models and Specs" for the H-34 is a 15 x 15 inch and the shaft is 1-inch diameter x 50.75-inches long. I believe the OEM shaft was bronze.The three-blade is significantly more expensive than the two-blade but should have less vibration. This can be discussed with PYI (link below). They're good people to work with. I went with the two-blade on our H-35 over 12 years ago and it's worked just fine for me. To further reduce vibration suggest changing out the bronze shaft with a stainless one and ensure that it is "true".The pitch is adjustable in increments on the Max-prop and the instructions will say what the pitch is for a paticular setting. I pitched mine up one notch and the black soot on the stern essentially went away.Simple to use; after the sails have been hoisted and trimed just turn the engine off and shift into reverse - the prop will automatically feather. Great addition to the boat and no sail changes are needed!Oh, and don't let your zincs wear out.