OMC Stringer Electric Shift Bearing problem

[Cody1234]

Greetings

I have a V-240 with a OMC electric shift. I rebuild the Ford 351 bored and stroke for about 350HP and more torque.

The upper bearing on the lower sterndrive seized up. I replaced all the bearings, shimmed to factor tolerences, and refilled with the OMC premium fluid C per the manual.

I ran it for about and hour and burned-up the upper bearing again and broke the shaft.

Any ideas why this is happening?

Thanks for any help