The Foley website refers to this number on the basis of some customers that were replacing or rebuilding their transmissions at about 1000 hours. https://www.foleyengines.com/tech-tip-106-zfhurth-gears-dollar-hour-gear/   

 Foley provided a list of reasons that some people were getting such poor service life such as:

1.  Mating a marginal or undersized transmission to too large of an engine.

2.  Allowing these gears to get low on fluid.  The point being that these gears hold so little that even a small loss is critical)

3.  Saltwater corrosion eating through the case.

4.  Prop wraps.

Basically reasons that with some reasonable care, maintenance and a proper initial installation that can be avoided.  I am getting the impression that good maintenance and coolers are pretty important to the life of these boxes.    It appears that on my boat that Amel oversized the transmission a quite a  bit and I have heard from a number of other Maramu owners that have as many as 10,000 hours on their transmissions.  

Best,

James

SV Sueno

Maramu #220