It's an electric motor
that drives a worm gear
via a belt (the belt is a standard component: 124L, half inch wide). The manual back-up works directly on the final axle (the one on which the chain gipsy and rope
drum are mounted). It is a very simple construction and easy to service/repair yourself. Ours is 34 years old (original equipment
on our Hallberg-Rassy 41) - we just rewired it, changed the belt and did a strip/clean/paint/reassemble job. The gears seem to be good quality; look like new. The housing is made of alloy; if threads have corroded too much, there is enough space to drill/tap new threads. Our only problem was the alloy rope
drum that is frozen on the axle.