x dimension
 

the measurement for x dimension means, let say 17" would that mean from botton of boat up to center of the crankshaft 17" ?

The 17" would be from the bottom of the hull to center of the crankshaft.

ok thank you Griff.

Probably wrong....I thought X dimension is relativity between centerline of "0" trim prop shaft and hull bottom directly in front of drive nose cone. Subject to prop design being surfacing or submerged, the X is usually adjusted up or down.

No, thats prop shaft depth. Griff describes x dimension correctly. Many people when refering to prop shaft height erroniously refer to it as x dim.

Thanks Guys....Griff My Bad....Blue Thunder, you're correct, had to look at the Mercury Book.

hey griff,
i understand what you are saying here however i have a question for you.

lets say with a V bottom twin application. do you measure straight down like with a plumbob from the center of the crankshaft to the point where it intersecs at the V?

or is it still considerd to be measured to the very bottom of the V?

The X dimesion i most often i refer to is the drive / prop height at 0 trim and measure straight upward to the bottom of the hull from the center of the prop shaft. i am not disagreeing with you at all just wanted to clarify the correct way of measuring the true X dimesion.

thanks for your help in advance.

john

Is there a simple way to measure the X dimension with the drive still on the boat?
Thanks,
Bob

It is still measured from the bottom of the V, as far as I know.

If I remember correctly, The actual X is 9 1/4 inches higher than the bottom of outside transom assembly.

You want the propshaft parallel with the bottom of the boat when measuring.

The propshaft depth is really what is most important anyway. It is also much easier to compare and measure. Most single engine V's are going to have an X around 17-18" an dthat will put the propshaft about 4-5" below the hull.

Thanks Griff!! You are a true asset to this forum!!

Yes it is straight down from the cl of the crank to the edge of the transom. Not to the bottom of the vee.

I was not sure, so this could easily be correct.

when i was working with gellner to determine drive heights / prop size among other things i was instructed to lower the dives to a neautrual position - perpindicular to the transom and then determine from the front side of the dirve where the center of the prop shaft is and then measure staight upward to the point where you meet the V. this is the measurement he was looking for anyway. it was difficult to my measurements came in somewhere between 11 to 12". don't remember off hand and am not at the shop. i would imagine this measurement would be affected by both the true X dim. and also the degree of the hull bottom. dean seemed to think my drive heights were on the high side however the boat pops out of the water effortlessly with out much slipage.

regardless i am always up for any new knowledge on the issue.

"X" dimension is the distance "on" the transome from the intersection of the boat bottom and transom ( drive location) to crank center to place the prop shafts at the desired heights.
This "X" dimension ends up being the "measurement" as you have to draw a line extending your running surface and then measure straight down from the crank centerline until the two lines intersect. "X-dimension" and "Prop-shaft height" are not the same thing.

Center line to prop shaft center line when trimmed parallel with the extended hull keel line and measured at right angle to that keel line. (not along the slanted transom) Prop shaft height (which is the dimension that most prop builders want to know in order to set you up with the right prop) is the distance, again measured at right angle, from the extended hull keel line to prop shaft center line, and again trimmed parallel. Don't make me come up there....

LOL... why not come up here the weather is awesome. summer is finally here. it's been in the 80's for over the last 3 weeks now. i know what your getting at when you say parallel. i have obtained basically the same results by doing it a little differently. however you have explained how to obtain these measurements very well. this will go down in my boat bible.

so what does it mean when someone says they have an aggressive X dim.?

well said , I will have do one this spring taking a use twin and making it a single:eek:, but it will have a DEAN GELLNER 572 in it:coolcowboy: and konrad drive. or if I hit the lotto have Dean build a twin motor then I would need a bigger boat by a few ft. art

Maybe I am misunderstanding what some of you are saying, but the "correct" definition of "X" dimension is the dimension "on the boat transom" from the bottom to the crankshaft centerline location. It refers back to simple right angle trig, looking for the hypotenuse of a right triangle, commonly referred to as "X" in the formulas. When you look at an X dimension chart, you input your desired propshaft dimension from bottom and your transom angle relative to bottom and the chart will give you the dimension to help place the cutout in the boat to get the desired propshaft location.
Now that is the technical definition, but many, including myself, interchange x for propshaft position relative to the bottom.

Sorry for the late post! I forgot to look at the second page of postings and "Velocity Vector" already put in the correct definition!

This can come in handy when trying to measure your X or your propshaft depth since it can be "awkward" especially by yourself.

Measure to the bottom of the transom assy and add 9.25" and that is your X. Now subtract your X from 21.825" and that will be your prophaft depth.

Example:

From the bottom of my boat to the transom plate is 7.875". Add 9.25" to that to get an X of 17.125". Subtract that from 21.825" to get 4.7" propshaft depth. :D

An aggressive X is a X that is higher than most boats of similar design.

If most Pantera 24s have an X of 17" and I am running a 19" X I would have an "aggressive" X.

Most people are incorrectly referring to propshaft depth when they say X dimension. But we're all used to it now! :D