Prop Help

[svfraidknot]

I need to replace my starboard prop on my 42 solaris my motors are 50 hp yanmars.
It is a right hand prop and my shaft is 1 inch. I measured from shaft center to end of prop and is 6.5 inches " so 13 inch prop" . When i measured the height of the prop "hub" is 2.5 inches. There is no number on the hub of the prop where there should be a pitch ? The only number is on the end of the hub the right hand prop number is t 284 left hand is t 285 .
Is there a way to figure the pitch with the measurements i just gave or can anyone shed any light on the two numbers i have ?? any help and or advice would be appreciated .

[DougR]

You can make an approximate calculation of the pitch by laying the prop on a good flat surface, supported by the hub with the blade face ( pressure side) up. Measure the angle between the flat surface and the blade face about 75% of the blade length distance out from the hub. Plot this measured angle on a large piece of paper and extend the lines out a distance equal to the circumference of the 75% blade length circle.
The distance between the two plotted lines at this point will be very close to the pitch of the propeller, because this distance represents the distance which the propeller blade would "screw" itself thru the water if there was no slip.

A more productive method might be to take the prop to a decent propeller shop. They can measure the pitch accurately with a prop scan machine or pitch blocks, and they can also check that it is really a 1 inch shaft with American taper or a 25 mm shaft with metric taper.

DougR