U-Joint stress -- what's the difference between.....

[Cptkid570]

I was watching an instructional youtube video that I'd come across in another post (not a good video) and a lot of comments were criticizing the poster for running his engine with the drive up. It got me thinking .... what is the difference between running your engine with the drive up and running your engine while turning the boat? Don't they both put a bend onto the u-joint? I don't think the angle would be too too much different. The U-joint doesn't care if the angle is bent up or bent sideways. A bend in the u-joint is a bend in the u-joint.

The only thing I can think of is that if you run the engine with the drive up, then it is bent for a longer time period whereas when you are driving the boat, you don't run on a turn for very long periods of time.

Just wondering and looking forward to any comments...

 

[Bondo]

I was watching an instructional youtube video that I'd come across in another post (not a good video) and a lot of comments were criticizing the poster for running his engine with the drive up. It got me thinking .... what is the difference between running your engine with the drive up and running your engine while turning the boat? Don't they both put a bend onto the u-joint? I don't think the angle would be too too much different. The U-joint doesn't care if the angle is bent up or bent sideways. A bend in the u-joint is a bend in the u-joint.

The only thing I can think of is that if you run the engine with the drive up, then it is bent for a longer time period whereas when you are driving the boat, you don't run on a turn for very long periods of time.

Just wondering and looking forward to any comments...

Ayuh,.... Even at dead-on straight, U-joints stress, hence the reason for the double cardan joint,... Close, but not quite a CV-joint,....
Not runnin' the drive Full up saves stresses on alota parts besides the u-joints,.... gimbal bearin, coupler, All of it, so Why do it,....
When turnin', it's usually short, 'n usually slowly, not Wot,... Slight turns of course ain't so bad, 'n who's runnin' Wot in a full lock turn,..??

 

[tpenfield]

The drive will tolerate being run up in the 'tilt' range at a very low speed . Full tilt would tend to give the outdrive a greater bend than turning, but it is probably a close call. Under normal operating conditions, when you turn, you are not turning the outdrive all that much.

However, if you want to hear the u-joints complain, just do either of those 2 things. hard turn at above idle speed or running at idle in full tilt position.

So, it is the sort of things that you can do for short durations at low speeds and get away with, but not an everyday thing.

 

[Cptkid570]

Thanks guys. That's what I figured.