According to the 2003 Mercury Mountaineer Owner Guide :
Both the 4.0 liter SOHC , V6 and the 4.6 liter V8 engines have the Motorcraft
BXT-65-650 battery
( that's BCI group size 65 , 650 cold cranking amps )
On a 1997 Mercury Mountaineer : It came from the factory with either the Motorcraft BXT-65-650 battery ( or the optional Motorcraft BXT-65-850 battery ) ( that's BCI group size 65 , 650 or 850 cold cranking amps )
it is a 29 mm hub nut socket
8"
You don't say which model year of Mercury Mountaineer but they have all used the ( BCI group size 65 battery ) such as the Motorcraft BXT-65-650
You don't mention what model year of Mercury Mountaineer so I was looking at various model years The Owner Guides show that the Motorcraft BXT-65-650 battery was used most ( that's BCI group size 65 , 650 cold cranking amps ) * some model years have an 850 cold cranking amp battery shown as the optional battery
See sources and related links below to lookup bulbs for any year mercury mountaineer.
Each remote takes ( 1 ) coin style battery ( CR 2032 ) or equivalent according to the owners manual
the four door speakers are 6x8 and the sob if you have one is 8"
The sub woofer size on a 1999 Mercury Mountaineer is 5 inches by 7 inches. Speakers are located in the front and the rear of the vehicle.
On a 2007 Mercury Mountaineer : Open the drivers door and on the end of the door ( or the latch pillar ) you will see an information sticker that shows the original size tires on the vehicle from the factory
5x7 in both front and rear doors.
21 U.S. gallons ( 79.5 liters )