Im not convinced, prolly cause thats not what I want to hear. My boat runs right about where it should for its size, weight, and power. My big problem is getting positive trim. I would think that with a deeper prop, more actual trim (like what is shown on the trim guage) would be required to lift the nose. Kind of like using a longer breaker bar on a nut. You can apply more force but have to move the wrench further. I think that the reverse of this is limiting the amount of trim I can get. The force applied to the prop by the weight of the bow is increased becuase of the length of the outdrive below the hull. The prop cant hold the bow up and blows out. Im hoping that the four blade will hold the water better resulting in the ability to increase positive trim. I just purchased the prop from a member here and will know as soon as it arrives.

If you need large amounts of trim to carry the bow of your boat, then the rev is a prop that you could try but I wouldn't buy it. You'll need a higher rake prop than the rev. The machs arn't the best props on the planet, but I'd be trying the sterndriver.

I heard/read that the 'X' dimension is the distance from a horizontal line up from the V which measures the width of the cavitation plate or about 5"- from that line to the crank centerline.

That is draw and move a horizontal line up from the point of the V on the transom until the line is 5" wide and then measure from there.

Same question and so many answers. What is 'X' dimension? Too many definitions and confusing.

I like a better measurement of propshaft location in inches above or below the 'V' point or for cats the bottom of the sponsons.

I too have heard of that method...guess it depends on who you are talking to as to whether it's correct or not.

Well, time to test my memory again. According to what I remember from the Merc layout templates, the X dimension according to Merc is the distance from the crank centerline to where a vertical line through the crank center intersects the bottom, measured on the transom surface. On a single this would be the bottom of the V, on a twin this would look like a rectangle when drawn on the transom.

As boat transoms are usually built at an angle of 10-14 degrees from vertical, the length of a line drawn on the transom (X spec) will change with transom angles to produce the same crank/bottom distance.

As the prop / crank distance various on the different drives, so does the recommended X.

The real thing that matters is where the prop is in relation to the bottom, that is what I really look at. As I can barely remember breakfast at lunchtime, I don't even try to remember the X spec for the different drives. I just want to know where the prop is. It also is very difficult to measure once the engines are in. I scribe a small line at the crank C/L that is visible once the drives are mounted.