No , the 5.0 liter V8 engine in a 1998 Mercury Mountaineer has ( 1 ) timing CHAIN
Timing chain.
In the 1998 Mercury Mountaineer : The 4.0 liter SOHC - V6 engine has ( 3 ) timing CHAINS The 5.0 liter V8 engine has ( 1 ) timing CHAIN
You can check on eBay.
On a 2002 Mercury Mountaineer : The 4.6 liter V8 engine uses ( 2 timing CHAINS / 1 CHAIN to each cylinder head )
only when it begins to fail.
chain
locate timing chain guides.
The 5.0 litre / 302 cubic inch V8 used in a 1999 Mercury Mountaineer has a timing CHAIN
The 4.0 liter SOHC , V6 , has ( 3 ) timing chains and the 5.0 liter V8 has ( 1 ) timing chain , if that's what you are asking ?
To set the timing on a 1997 Mercury Mountaineer with a 5.0 engine, you'll need a timing light tool. Connect the timing light to the battery and number one spark plug wire, then start the engine and point the timing light at the timing marks on the crankshaft pulley and timing cover. Adjust the timing by loosening the distributor hold-down bolt and rotating the distributor until the timing marks align with the correct specification, then tighten the bolt and recheck the timing.
Timing chains are designed to last the life of the engine. They are normally replaced during a complete engine overhaul. Unless the chain becomes noisy no maintenance is required.