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x-dim - Improper Lingo?
Can someone tell me the proper method of checking current "X" dimension?
Actually I have heard of two ways to measure X.
The reference is from the crankshaft center line to the bottom of the boat.
The two differernt methods defined the bottom of the boat differently.
One was to the deepest point on the bottom of the V (and I am refering to V bottom boats, only).
The other way they measured a certain distance from the center of the hull out to some point. I dont remember how it was described, maybe to the edge of the pad (if it had a pad) or to the first strake or what ever. Then the deepest point of the boat was an average between these two points and the deepest part of the V. I know it wasnt all the way out to the side of the transom, just a short distance out from the centerline.
My point is that, it was confusing to say the least. I measure to the bottom of the V and call it good. Then when I reference some other boat I measure it the same way to keep things equal.
There may be a Nautical definition of the X dim. But crank to bottom of the V is what I go by.
Now if you change the lower to a shortie, then you have to include that in your comparison, because to keep apples to apples X dim doesn't include the length of the drive.
Thats when "propshaft below the V" distance comes into play.
Hope this makes some sense. It's all relative. The higher the propshaft is, the faster you will go until you cant get on plane or hold the bow up at speed.
Measure from the bottom of the V to the bottom of the transom assembly and the add 9.25 inches. That will get you within an 1/8" of your actual X dim.
The x dimension is the measurement used to cut out the transom. It is hard to measure once the assemblies are in place. There are two methods used by Mercury to determine cut out location.
One the 90 degree tool method and chart that takes transom angle into account.
The actual number refers to the point on the transom where the Vertical Center line meets the Horizontal Engine Crankshaft center line.
It is easier to think in terms of prop shaft relative to the bottom.
For example on a #6 18 5/8" X puts prop shaft even with the bottom. with zero spacers.
17 5/8 would be 1" below bottom
19 5/8 1" above
Once everything is assembled measurements and with drive parallel to bottom the height of prop shaft relative to the bottom are easier to work with when comparing and adjusting.
I get the basic concept but have two questions:
1) When you say drive parrallel with bottom, you do mean that it must be trimmed to get it that way since when the drive is in its full down position it is not parrallel!
2) What exactly do you mean by bottom of boat? lowest point of the hull or the parrallel surface which is in line with the drive shaft?
Yes Scott Thanks,
Trim drive parallel, a digital level makes it easy.
Measure at engine centerline
This is nice to get right... some say that they raise their X-dimention when they change from stock Bravo lowers to short sportmaser lowers. This must be wrong then, as the X does not refer to the propshaft.
What you tell me is that the X-dimention is the distance from where the propshaft comes through the transom and down to the point where the transom and hull comes toghether, or down to the bottom of the boat (vertically down).It is a little complicated as most boats (we are talking about here) has two engines/drives or more.
How is this discribed on a boat with triple engines?
Its kind of a play on words.
Yes, a shortie acts like it has raised the X.
The X is for initial rigging.
The relation of the prop shaft to the bottom is a better way of discussing and comparing set ups once the boat is assembled.
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