The pump (the bolts backing out specifically) falling off, has nothing to do with what kind of engine its mounted on, like RR says. THe pumps are all the same.
Its just an extremely harsh environment, lots of vibration and force from the h2o.
As far as the never seize and electrolysis, all the pumps I have owned have had sacrificial zinc anodes on them. I guess thats why I have never experienced THAT problem. The dissimilar metals still require some sort of lube/never seize to avoid inevitable corrosion.
I have had about everything else happen that could.
As far as manufacturers of the engines, it changes yearly. Just like in the auto industry (another industry I know just about nothing about), most manufacturers have their hands in everyone elses pockets in one way or another.
You ahve to look at their quality control programs for their finished products. Yamahas is ranked #1 in the industry according to several different surveys. (A couple different mags I read). That could change year to year.
I think that in this day and age, with proper maintenece, any of the outboards should run great for many years. I just have an affliction for Yamahas. In Sitka, there are about 150 to 175 charter boats running the snot out of their engines day in and day out. They ALL run Yo-mamas.
has anyone ever listened to the noise put out by a Yamaha jet vs. a Merc? You need earplugs to run the Mercs. Not sure why, but they are WAY louder.
At any rate, thats my 2 cents.