[Note: Corrosion is more than just a nuisance - it can cause a fire. Please consult with a qualified marine electrician on all installations and modifications]
Having just killed a SEVCON controller due to corrosion I think I am something of an authority. I thought when I installed the motor that having a stainless bolt with a brass nut connecting an aluminum wire lug to the controller (and basting the whole thing in seawater) might just be a problem...I was right.
Connections should be made with heat-shrink adhesive-lined (marinco or similar) connectors. All wire should be marine-grade tinned. All areas where the wire passes through bulkheads should be provided with chafe protection. Wires should be secured to avoid vibration.
Stainless steel and aluminum are a real problem - anywhere you need to make this connection you should use Tefgel or some similar anti-corrosion compound - otherwise the aluminum will degrade - the first problem you'll see is that you won't be able to unscrew the bolt.
The magnets in PMG motors are also subject to corrosion:
"Rare earth magnets are extremely susceptible to water, and literally
foam with oxidation if (when) the plating develops pinholes. Poor plating
protocol by itself will fail the magnet. Bonding magnets results in the plating
being well fastened, but the strength of the bond is then only as strong as the
plating-magnet interface. To further complicate matters, the magnet has only
half the thermal coefficient of expansion as the steel mounting plate, so every
thermal cycle works the magnet-plating interface just a little more."