Spare Parts....which ones, and how many?

Ohhhh yes, it's almost a 2 person job to change them. One person to hold the filter, full of fuel up there against the spring pushing it down, and another one to make sure the bowl gasket is in place and to try to line up the T handle and tighten it. The funny thing is someone told me they were invented by the guy who invented the Racor's after he invented the racor and sold off the patent. Talk about a huge step backwards.

And what spec does "high speed gear lube" meet that good old fashioned gear lube doesn't?

I meant to say "High Performance gear lube". Mercury designed it for their high rpm engines with higher propshaft rpm lower units. Race outboards turning 8200 rpm's and such. I think it is synthetic based. Many outboard and stern drive race guys swear by it in everything from Mercury's to Yamaha's. But in America, you are welcome to use whatever gear lube you'd like!

Here is from the Mercury site:
Engineered to provide maximum protection for sterndrive and outboard lower units.
■Exclusive formula is engineered to provide extended gear life in extreme conditions including high-speed and high-horsepower applications.
■Extensively tested to provide excellent protection against corrosion and excessive wear.
■Specifically formulated to help prevent failures due to water entering the gear housing.
■Extreme pressure synthetic additives protect gears from metal to metal contact.

I don't make the motors nor formulate the lubricants. A company like Mercruiser says to use this lubricant, I use this. I know that voiding warranties for using someone else's lubricants has been successfully challenged in the auto industry. I don't recommend people become the test case with marine warranties, especially when it comes to outdrives or IPS units, etc.. And yes, High Performance Gear Lube.

Mercury states that it does not void warranties when used in any of their outboard or stern drive lower units.

■Provides warranty protection for all Mercury MerCruiser sterndrive and Mercury, Mariner and Force outboard lower units.

As for using it in Volvo's well maybe a little bit different. I do know that stern drive and outboard mechanics that race them and are big dealers swear by it in all makes that they service.