I have a 1991 70 H.P. Nissan motor. I removed my prop in hopes of getting it repaired during the winter months, it has some slight damage to the blades. The only markings at all that I see on my prop is the number 12 that is embedded right into the side of the prop. Would this be the pitch of the prop or the diameter of it? There are no other numbers or letters anywhere on the prop, inside or outside. If this 12 indicates the diameter, how can I figure out the pitch? I assume a prop shop can figure that out when I take it in for repairs,, correct? I am thinking they can tell me both, the diameter & pitch of the prop that I have, but I am not sure, Thanks!