Actually, the replacement was simple and without surprise. The engine was moved just a little.
We installed a separate water intake and are very glad we did: we can now open and close as well as filter: we found debris of plastic bags in the heat exchanger
of the other engine that still gets water from the saildrive. Also, the water tap on the SD50 is as bad as the one on the SD40: it gets stuck in less than 6 months.
Are we happy about the change? not particularly, but we had no choice, the old SD40 had taken in water massively through a bolt broken (and hidden) by an incompetent mechanic
. The SD50 is basically the same as the SD40: a bad piece of mechanic
; we still expect it to slip anytime after 600 hours which we have just reached.
The only visible improvement is the easier and quicker way to pour new oil
through the bigger opening. As for the slipping, we learned a lot about the innards of the SD after the change: we completely dismounted the old SD40 and kept all the spare parts
from it we might need in the future. That is probably the best advice we can give to anybody doing the same. So when, a few months later, our remaining SD40 started slipping, we bit the bullet and went through the whole lapping thing by ourselves.