minn kota broken shaft transom mount

[rjfalkiner]

I have a new minn kota DRIVE UNIT not transom mount (edit) trolling motor shop mounted properly on a mercruiser. The prop shaft broke fairly cleanly right at the mid point of the shear pin hole after less than about 3 weeks of boat operation (skiing cruising etc.) with only a few hours trolling motor operation with no prop strikes. The trolling propeller simply fell off during normal boat operation (I thought the battery was dead, and during re-charging noticed that the propeller was missing...battery was still fully charged, and trolling motor still operated quietly with no vibration). It was very quiet during trolling operation (was able to sneak up on a beaver dam and watch a beaver and her pup a couple of days earlier, for example).

to me it looks like a progressive crack formation on both sides of the shear pin hole, and when it got to less than about 1/16 inch metal both sides, it snapped cleanly. It left a bright shiny metal area both sides of the shear pin hole forming a "cross" about 90 degrees to the shear pin hole (vibration induced cracking????).

I checked the clearance on plane and the trolling motor prop would have cleared the water by several inches while on plane. This makes me think that this happened during normal boat operation while getting up on plane and slowing down??

anyone else had this happen?

 

[Barnacle_Bill]

Re: minn kota broken shaft transom mount

If running on plane your T/M should be completely out of the water and in the stored position. You probably hit some waves and didn't realize it was hittin the motor. BTW, those shafts are guaranteed.

 

[floatingwoody2006]

Re: minn kota broken shaft transom mount

Yup.. If im not mistaken, those composite shafts are guaranteed for life. At least mine is..