?? X Dimension

[ken]

ok ok calling all you outboard V20 owners.........i was asked by the guy that is going to rig my motor when the boat is ready. WHAT the X dimension was?????? he said it was the distance from the center of the bottom of the boat to the center of the prop shaft. had never heard of that before.........................if by any any any chance anyone knows. i'll owe you a beer. all kidding aside if anyone knows this one it would help.
thanks ken

[macojoe]

My guess is that he is asking you what shaft leanth you need?? Which is the top of transom (center) to bottom of the boat.
Or from the motor bracket were it sits on the transom to the Cavatation plate (above prop)
This will give him the shaft leanth of the motor.

I hope this is it?? other wise yopu will need some one wiser then I!!

I have never heard of that measure before?? you can change the distance from boat to prop by timming the motor??
When you find out let us no, as I have never heardof this before and I converted my boat to a outboard motor and never considered this??
But it works fine.

[chumbucket]

I've never heard of needing to know the distance from the center of the bottom of the boat to the center of the prop shaft. I have heard of the "X" dimension though. I think MJ is on the right track. What I thought it was (and I may be wrong), is the dimension from the top of the transom (at the point of the motor mounting) to the lowest point on the keel. The motor needs to be set at the correct height which generally puts the cavitation plate at approximately 1-1 1/2" below the keel.
You may want to ask the question on The Hull Truth site or iboats.com to see what they can offer for assistance.
Otherwise, you'll have to ask him to clarify.

[ken]

hey chum,
i think you got it. he said the lowest point of the keel to the center of the prop shaft. that is what the x dimension is..................i guess..........you have to excuse me i'm polish, sometimes it does not comput ;D
ken

[macojoe]

Well I thought the prop is under the boat??
The prop shaft and keel never are inline with each other! The cavation plate is in line with the keel.

[ken]

maco,
i guess you take a straight edge to the bottom of the keel and extend it to the lower unit, then you measure from the straight edge to the center of the prop shaft. that is how it was explained to me. ( i think ) if this is the only problem i have i'll be happy
thanks ken

[macojoe]

I am glad you found out!!

Now tell me what the heck is that measure for?? If the cavation plate is even with the bottom like it is supose to be what that measure mean??

Not trying to start anything but I really like to no what this has to do with the price ogs in Mass. ???

[chumbucket]

MJ, that's the whole point. The cavitation plate is NOT supposed to be even with the lowest point on the keel. It's supposed to be a little below. 1"-1 1/2" I believe.

Hey BTW, not to hijack this thread but, MJ, do you read any other sections on the site besides this one? I posed a question for you in the "Off Topic" section. ???

[macojoe]

I try to?? If I see a post of the day. I come here 20 times a day and look for new post. I must have missed it.


Any way I am still wondering about this measurement??????? You no I am not the brighest light bulb in the bunch!! :-[

[chumbucket]

We know that! That's why we try to be patient with you. ;D ;D ;D

[ken]

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]

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

[macojoe]

Mine is even and works just fine!!

[Airslot]

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]

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

[Airslot]

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]

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]

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]

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

[Destroyer]

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? :head:

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. :beer:

[spareparts]

Airslot nailed it, he gets an extra cookie for using the proper term antiventalation plate, well done :beer:

[phatdaddy]

you guys must really be snowed in, re-hashing threads from 04 i hoping for a quick spring so we can all start burning gas soon.

[spareparts]

I'm allready burning gas, I'm at least a week behind in work, if the weatehr would cooperate, i'd be golden