Thanks for replying.
The motor seems to be in full strength so I (perhap mistakenly) discounted that possibility.
The problem: the wipers stop mid sweep for around intervals of various length (on any of the three speed settings and even on the squirter setting)and then continue.
I've just acquired a wiring diagram which refers to the combination switch housing (located behind steering wheel) the "washer switch" and the "wiper speed switch". Since the wipers stop in this manner when on either any of the three speeds or when the squirter setting is operating, this implies the problem resides with something common to each of the two switches.
In short: do you think it could be the motor afterall (even if it seems powerful)? Open to suggestions!