repeated drive shaft failures revisited.

[misery]

Hi folks. So last season I had the misfortune of having the second drive shaft break in 2 seasons. I posted on here about it and got some good responses as to why I am being plagued with this problem. I am about to mount a used lower unit on my motor, ( 1986 evinrude 90 hp), but I am nervous to do so for fear of breaking another shaft.
The last shaft cut off just below the impeller, right about where the top seal for the gear case rides. The shaft looked like it had small hairline cracks radiating inwards, but it is difficult to tell as the ends banged together a bit before i got it shut down.
In my previous post about this it was mentioned that my gearcase might not be parallel with my motor and that would cause undue stress on my drive shaft. It was also mentioned that the factory manual has a procedure for checking for parallelism. Here's the rub. I cannot for the life of me find a manual specific to my motor.(e90tlcdc). If any of you good and helpful souls out there in happy boating land could at least paraphrase the procedure for checking parallelism that would be incredibly helpful.

 

[Fed]

No Title

1988 Model 90 HP.

 

[misery]

Thank you for the response Fed, I will look into this.I was thinking about this problem and i wondered if you have to have the motor trimmed down(vertical) when tightening the lower unit up or does it matter?

 

[Fed]

Being vertical is not something I've ever worried about.
The same drive shaft part number is used on motors up to 140HP so I think you might be on to something checking for straightness of the housing, it would seem to me the drive shaft on your 90 is not a weak link.

 

[Faztbullet]

Distorted housing will only wear splines not cause shaft to break....

 

[gm280]

WOW I would assume that it would take a lot of heat and stress to break such a drive shaft. And you have had two break. That does seem to break all odds in my thinking... Did both break in the same area of the shaft? :noidea: