Jay, take a VERY close look at the slots in those plugs. If they seem
deeper
in the center than at the edges, they're supposed to be removed with
something called a DZUS driver. My Johnson outboard's drain plugs are
like
this, and a normal screwdriver (which you can get at Sears, by the way)
will
mess up the slots.

I have checked the slot in the plugs, and they are the same depth from
edge to edge. This means I can use a regular screwdriver instead of
the special kind. Thanks for the warning though.

Jay, before you bother with Harbor Freight, have you simply walked into a
Sears store? I have tool # 41852. On the handle, it says it's a 3/8" driver.
When measured, it's just a hair under 1/2".

I was in Sears a couple days ago, and I checked all the screwdriver in
the store. Nothing was larger than 3/8", and yes I used a measuring
tape to check the width of the blade.

Jay Chan