Prop Pitch vs transom height

[ironlake2]

Looking at some of the race boats it looks like the top blade of the prop is always out of the water. If this is the case do you have to run with much more pitch with only one blade loading the engine.

[velox]

The answer is "sorta"
By raising the prop out of the water you get less drag. That "allows" you to run a prop with more pitch, resulting in a higher speed.

[Mark75H]

Norris should move this to tech

You have to run a little more, but not much ... probably an inch to a half inch ... and since props are often marked less accurately than that ... the general answer could be no. Sometimes prop makers mark a prop with numbers that they think are its comparable performance rather than which block it fits best.

what is more important than any pitch increase would be the actual blade shape and where the blade carries the pitch for running surfaced or semi

This is like asking an artist what colors need to be on a painting to make it "right" What works on one boat may not work on another identical boat, one person's idea of "right" will be different from some other's

[ironlake2]

thanks guys for the answer. Now what are the cleavers designed for as far as what type of boat prop height etc.
Do the prop jet motors give the small hubless props a problem in taking of with all the bubbles from the exhaust around them?
I had a michigan opc prop on a merc 40 hp and it had a terrible hole shot as the motor just screamed until it planed off and then it would grap.

[Mark75H]

No, thru hub exhaust has almost no bad effects

High rake cleavers cause the bow to rise as if the motor was kicked out ... even when the prop shaft is pointing down in the back in extreme examples


Your old 40 OPC prop experience sounds like a set up problem rather than a problem related to the prop itself

[velox]

thanks guys for the answer. Now what are the cleavers designed for as far as what type of boat prop height etc.
Do the prop jet motors give the small hubless props a problem in taking of with all the bubbles from the exhaust around them?
I had a michigan opc prop on a merc 40 hp and it had a terrible hole shot as the motor just screamed until it planed off and then it would grap.

Back in the early 60's the E class OPC boats were running about 52/53 MPH, When the through the hub props came out we picked up about 4 miles an hour to 56/57.