?? X Dimension - Page 2

#11 03-20-2004, 08:09 PM

the reason for the x dimension is for performance. fuel, plaining, wot, handling and all that good stuff...............he said that the cav plate should be above the bottom of the keel, cleaner water less turbulence. oh oh this is getting scary. it almost sounds like i know what i am talking about. ;D

chumbucket · #12 03-20-2004, 08:53 PM

Above? I thought it was below but like I said, I was probably wrong.

macojoe · #13 03-21-2004, 12:00 AM

Mine is even and works just fine!!

Airslot · #14 03-22-2004, 05:40 PM

THe anti ventilation plate should be even with the bottom of the hull for your average installation. To fine tune your rig, move the engine up one hole at a time until it won't hang on at full trim, then go back down one hole. The idea is that most boats will run fine with the plate a little higher. The good side is that you'll be dragging less gearcase throught the water which gives better speed and economy. Make sense?

Airslot

macojoe · #15 03-23-2004, 12:44 AM

Less drag always makes sense!! I just never heard of the measure before??
See you do learn more every day!!
Thanks Airslot

Airslot · #16 03-23-2004, 01:25 PM

This was bugging me so I did a little more reading. Typically, "X-Dimension" is a term reserved for use when discussing stern drive mounting height. It is the relationship of the prop shaft centerline to the boats running surface. This is generally difficult to modify in a sterndrive. They also make drive spacers for more setback for high performance use. When mounting outboards, the most impotant measurement is shaft length. It must match the transom height which, is typically 25" for V-20, but there are boats like my V-20 which has a 20 inch transom. For anybody wondering, raising the motor one bolt hole is the equivalent of 13/16". For those running brackets, a good starting point is to raise the vent plate 1" above the hull bottom for each 12" of setback.

Just some more info.

Airtslot

macojoe · #17 03-23-2004, 02:43 PM

I am 28 inch set back that is aleasat 2 inches.
I heard about that when I was putting the bracket on. But I thought it was to mount the bracket up higher and I just did not like the bracket up that high on the transom. So I put it so that the 25" shaft was right and thats were it is.
I just went out to look to see were it is and it is kind of hard to judge as the bow is way in the air and the motor is all the way down, but looks to be about almost 2 inches above the bottom?? I don't rember doing that but that is were it seems to be so i guess i got it right?
I do alot of things by accident ;D

chumbucket · #18 03-23-2004, 04:55 PM

Good info Airslot. Thanks. I'll be needing that for the mystery project.
That's where I had heard the term "X Dimension" used before. When I repowered an I/O years ago. Very big, heavy boat. May have had something to do with why they guy decided to lower the leg. ??? ??? ??? Now I'm going to have to ask him because I'm curious.

randlemanboater · #19 02-11-2011, 09:35 AM

How did this get the the top of the list? Its from 2004!

Destroyer · #20 02-11-2011, 11:08 AM

I guess I'm showing my ignorance here, but I always thought that the professional that's installing the engine would know what the proper setting was for the "X" dimension. I mean, if they don't know, then how the hell should the owner know?

Personally, I'm pretty much with MJ on this one. I've always set my cavatation plate to be even with the keel, and then I usually sink it an additional inch lower for good measure. Might not be the most accurate way, but it's always seemed to work ok for me.