broken drive shaft

[pottord]

I have a 78 evinrude 25 hp short shaft motor, on the river Friday going to look for a new place to duck hunt. I was following the channel because I did not want to hit any thing flowing in the river. All at once the motor increased RPM and when I pulled the lower unit out of the water, the prop was not turning at all. After getting home and pulling the lower unit, I found the drive shaft was broken just above the splines on the yoke end that fits in to the forward/reverse gear. I visited the local repair shop and got a different shaft and the machanic put the entire lower unit back together.

Got the lower unit put back on Saturday and ran the engine is a trach can to make sure all was well. It ran and shifted ok....that leads us to Sunday.

Back to the river to hunt got about 3 miles up river and again then the same thing happened again. Got home and the drive shaft is broken.

Any ideas what could cause this type of problem?

Thanks for ideas and suggestions,

dp

 

[Mas]

Re: broken drive shaft

I do not know...but I sure feel for you! Seems to me that a whole list of other things would break before a drive shaft! Twice nonetheless!

Mas

 

[F_R]

Re: broken drive shaft

I do not know...but I sure feel for you! Seems to me that a whole list of other things would break before a drive shaft! Twice nonetheless!

Mas

And they will continue to break till you find out what is bent. The service manual spells out the procedure for checking the gearcase and exhaust housing on a surface plate and dial indicator. Whichever is bent is causing the shaft to bend back and forth every time it rotates, till it fatigues and breaks.

 

[Mas]

Re: broken drive shaft

Thanks FR! That makes a lot of sense!

Mas

 

[coolguy147]

Re: broken drive shaft

how do you break a driveshaft?