My yamaha engines get serviced at Tuckers Marine. Actually, that's a lie. They haven't needed any service LOL......but they are good guys. Neil will hook you up with any parts you need. They are in Apsley, but can ship parts. If its pumping water as normal, I wouldnt bother until you shut it down for the winter. If you have leaky lower unit seals, I'd get that fixed asap, or at least before freeze up.
S.