measuring X ????
 

OK someone must have asked before but it does'nt show up in a search....what is the proper way to measure my X demension?

The quickie method is to measure 9.25" below the gimble assembly to the bottom of the hull.

Cord!!!!!Dude where you been?hows that cat running????and thanks for the Quickie......

Don't thank me yet, 'cause I got it wrong. What I meant to say, was...Measure the distance below the gimble to the bottom of the hull and ADD 9.25" to that number.

Can't really say how the cat is running. I got it out briefly twice, and had a couple of things that I wanted to correct. It's been so cold, that I gave up and I'm having it winterized. Would have been nice to just run it next year, but oh well.

Good Luck !!!!post the results in the spring!!!

right on
 

Just measured my template and Cords on the money:D

Is that measured from the bottom of the transom assembly? Are all transom assemblies the same on the bottom? (do all of them have that plastic mercathode box)

No, you can take that mercathode box off. However, don't measure to that part. Put the tape tight to the transom, and it'll hit on the gimble near the gasket. Measure from that point down.

So what is the standard mesurement (CORD style). What is considerd hi and what is low. Mine is 6" from the transom asemble to the bottom of the hull. Witch gives me 15.25? Charlie

These numbers are for boats operating at 25mph and above. The x* number is the transom angle in degrees. You need to subtract 9.25" off the listed number for my quickie measurement to work.

16* 14 5/16"
15* 14 1/4"
14* 14 3/16"
13* 14 3/16"
12* 14 1/16"
11* 14"
10* 13 15/16"

For bravo boats that operate above 50mph the drive can be raised up to 3" above the listed number.

Blackhawk equipped boats start at a point 3" above the listed number and then can be raised 1 1/2" maximum.

extension boxes...
 

Cord, would you happen to know what the measurements would be to find the X when there is a Stellings extension box on the transom? thanks

Depending on what the transom angle was, Stellings told me that their box was designed for a neutral rise. I think that angle was 13*. If your transom is over that number the drive is deeper, if under the drive is higher.

Based off the the numbers that I have here, it looks like the adder number would be 11-3/8" when the box is on the center hole. The center to center distance between the drilled holes is 1". My box has the slots and the center to center distance is 2 1/2". These boxes do not have a 3" travel. The slot length is 3", but that's not the travel distance. Some creative measuring going on here...

Hey Cord, I measured my "X" the quickie way and the dimension from the bottom of the transom plate to the delta pad is 5.75". I run with a 2.5" short shaft drive. Does this put me into what you would consider an "aggresive" drive height? You seem to be pretty up on this so I thought I would pick your brain.
Thanks,
Craig

Vette,
What drive are you running that is 2.5" shorter?
Is it an Imco?
How does it plane off and on what hull are you running?
What prop pitch and number of blades?
I am considering going to a short drive and was curious as to what setup you have.
I know your running some big horsepower.
Thanks, Russ

stellings
 

Cord My stelling boxes are in the basement so i just measured them with digital readout gauge they read 13.5*
Mine are three hole type. just read stellings Bravo ad------
"When our stand-off box is bolted on using existing holes and the bravo drive is mounted onto the backof the box the drivehas been moved 12" back and 1" up on the X dimension. Whats more. on the X-dimension,the box is adjustable 1" up or down and has a 1" rise built into the box". I guess the information depends on who you talk to. or what ad they put out. I hope this helps

Kaama/Mark
 

Its me Bart/28 props
My X-dimen. is 16-1/4 with stellings mounted, I am 4" below transom/hull and am going with a 2" imco short drive. I have a call into Richie Sutphen. Eddie from smitty marine (Wazzup, 32ft Viper does 102-111) said I could be up one more inch any thing higher wont help.He is running imco boxes with bravo 30s. Viper boat has same bottom as sutphen. (26*V i had to measure it) he is running 30 cu x2=60cu more then me.:mad: :D :D :D :D :D

Bart/454hoho,

I always have known it was you bud. The transom on my 32'A/T does NOT have a notch, therefore I was told that with the Stellings boxes I would really benefit from a 2" shorter drive. Does your Sutphen have a notched transom? I'm quite sure a shorter drive will help on the speed, but is there much in the way of giving up any stability or planing off? Some guys are willing to do pretty much anything in the name of SPEED!!! Of course I like the speed too, but not at the expense of safety, handling and planing-----I'm sure there is a fine line and I don't want to cross it.

My Stellings boxes are mounted as high as I could get them on the transom. I was told to do this by the manufacturer. They (extension boxes) also have three positional mounting holes. With mine, I am using the bottom mounting holes so as to utilize the greatest heigth advantage I can get, so I can always lower the drives if I need to------did I say that right? LOL

BTW Bart, how's your boat coming along bro?

RLW, I meant a 2" IMCO shortie. I am confusing it with my dads alpha ss which is 2.5" shorter than the standard alpha. The boat is a 1990 Baja 210 Sport with decent HP. I run a 4 blade 14.5" x 29 Spinelli which I have seen a best top speed pof 97.8 and a 15"x 27 Quad 4 for a best speed of 96.9. I turn both props in the 6000 to 6300 RPM range. The boat has trouble coming on plane with 3 blade props, but it can be done. With the 4 blade props there is no prob.

Hoho-in regards to the stellings ad...I think we are both saying the same thing. From what I've been told, when you put a box onto a transom, the drive essentally ends up being 1" deeper. This has to do with the attack angle of the boat and the tansom angle. When stellings built a 1" rise into their box, they essentally cancelled the drop for a neutral rise...assuming a 13* transom angle.

I also want to confirm that the 13.5" dimension is from the drive centerline to the bottom of the box. I based my number off some drawings that I had here at work, and I didn't account for that rise that's built into box. I'm trying to figure where the additional inch came from.

Vette-If we run the numbers...5.75"+9.25"+2"=17" That would put you right at the top of the range for a 13* transom.

Vette,
Thanks for the information. Sounds like the Imco would work for me. My measuement is 5.875" from the Transom Assembly to Keel and I am running a standard length Bravo.
Boat is a 1989 27' Activator.

X dimension
 

If I remember correctly (it has been a long time) the standard X dimension is where a line extended from the engines crankshaft would pass through the transom when the drives cavitation plate is equal with the bottom of the boat. By moving everything up, placing the cavitation plate above the bottom of the boat, the X dimension (crankshaft centerline) is increased. This is a simple way to think of X dimension.
Higher X dimensions mount the drive up higher and out of the water decreasing the drag from the gearcase and increasing boat speed. This may come at the expense of cavitation in turns and acceleration cavitation from the prop sucking in air from above the water surface.
Please correct me if I am wrong!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

Kaama, My boat - no steps no beaks, etc, etc . The higher you place the drive the Slightly more speed especially when the football is out of the water (Less drag) BUT a Dennis stated the trade off is cavitation etc.
I had spoken to Chris Sutphen today (knows more then 90% of the people...) Max speed is when the prop shaft center line is 1-1.5 inches above hull bottom (record setting speed junkies) only one blade is in the water at any time, and the skeg is the only part of the drive in the water. The negative is handling which depends on boat bottom,k-plane,drive skeg area and on and on.
This high X-d is for max speed only,Sutphen did set (HONEST) kilo records The last record I recall was 85.96 with F2-50/stock factory 502 ci motors. I will agree with you mark and give up the speed for better handling.

Cord think we are on the same page. presently i have one stelling box and standard bravo 1 mounted on my boat. If i get a chance i will mount the other without the box and take measurements from center of prop shaft to hull bottom, like Kaamas im on bottom holes(box as high as poss).

Dennis 100% correct , X-d is what most performance boaters want to know, which depends on manfu., application etc..

Wette Vette I read all your posts. Very knowlegable about motors. When I have a chance I have questions for you,mark, findme and Eddie/smittymarine

Dyno sorry if I deverted your post, hope some of this info will benefit you.:)

If you've got a boat with three outdrives, do you have a XXX dimension?:D

Attn: Cord
 

Hey Cord,

I remembered your post when I found this:

http://www.performancemarine.net/bul...94/om94_06.pdf

Where did you get your information form? This is probably older (94?) than where you got your info from... what do you think?