DP-A prop shaft running out of true

[PCUK]

How can this happen? The two shafts are contra-rotating and yet there is a combined run out of around 1mm But the two shafts are running true to each other. No nasty noises and it all sounds and feels smooth. Baffling to me.

 

[spannerman]

Where are you measuring the run out, in all of the damaged duoprop drives I have repaired I have never had runout on the outer shaft as its too big and stiff , its always the longer thinner inner shaft that gets bent.

 

[PCUK]

Thanks for your interest To be honest, so far it is only visual although it looks as if both shafts are running out of true together. I'll get the dial gauge out tomorrow and have a proper check.

 

[volvopaul]

Inner shaft bent .

 

[PCUK]

Thanks Paul, I expect you are both right being the forum outdrive Gurus! I don't suppose either of you have a second-hand straight shaft in the spares box?

 

[PCUK]

Right, here are my findings. On the inner end of the thread (about an inch from the end of the shaft) on the smooth area of the small shaft there is about 50 thou' of run out. On the outer shaft on the smooth area ahead of the splines (about an inch and a half from the housing there is about 10 thou' of run out.
I've attached a video which may give you an idea of what I'm talking about.
Google Photos