Silly Question...

[WillyBWright]

The "X" dimension refers to the HEIGHT of the drive on the transom. Correct me if I'm wrong, but isn't the X axis Horizontal and the Y axis Vertical on a graph? Shouldn't that be the "Y" dimension?

 

[daveswaves]

Re: Silly Question...

They tried labelling it "Y" but the guys in the boat factory kept getting in fights when the installer asked how high should I put this drive and the engineer kept saying "Y"

 

[Don S]

Re: Silly Question...

I like daveswaves answer better, but actually the X dimension is the horizontal dimension through the centerline of the crankshaft.<br /><br />Here is a Volvo drawing that shows the x dimention in relation to the crankshaft centerline.<br /> Drawing

 

[rabidfish]

Re: Silly Question...

It's true, "X" is the horizontal axis. The figure is the dimension from the bottom of the boat to the "crankshaft" centerline. (Where is "X" located?).<br /><br />My question has always been: What difference does that make? The dimension that matters is from the bottom of the boat to the "propshaft" centerline...<br /><br />That just always seemed weird to me.

 

[rodbolt]

Re: Silly Question...

on an outdrive the relationship between the propshaft and crankshaft is fixed. the "X" diminsion came into play by the way the centerline is found. when you lay out all your marks you will have two near the transom top and two near the transom bottom. if you measure diagonaly from port top to stbd bottom and stbd top to port bottom it resembles an X. if all is correct the intersction of the two diagonal lines is the X dimenson or the crank centerline. there are multiple reference points taken from the X diminsion on a new package installation. the x diminsion will change with transom angle. the engine bed is laid out from the X diminsion. on a lathe Z is to and from the spindle and X is horizontal. so the terms all just depend. especially on new hull layout its a lot more to worry with than just prop shaft to hull. especially laying out twins.

 

[rabidfish]

Re: Silly Question...

Depends on the application: The propshaft/crankshaft centerline is not always the same dimension, nor is it always "fixed". (read: Bravo1 vs Bravo2 vs "Blackhawk") All have the same "X", you know the rest...<br /><br />On a sterdrive we consider the "X" to not be adjustable, and it technically isn't. But the propshaft centerline can be adjusted (only with aftermarket performance parts)to gain performance advantages much like a "jack plate" on an outboard. <br /><br />Racers have been doing this for years. Many, with the experience, simply mount the package in the "right place".

 

[Don S]

Re: Silly Question...

Yes you have a different X dimension on different drives. That X dimension is used to get the best location of the cavitation plate. There are differences in the B1, B2 and Blackhawk drives, therefore different X Dim.<br />When the angle changes so does the actual height of the cavitation plate.

 

[WillyBWright]

Re: Silly Question...

Now it makes sense. Thanks Gents.

 

[rodbolt]

Re: Silly Question...

clear as mud. but when we developed the swan points from strictly outboard to stern drive we had some factory engineers that showed us a lot and why.