Re: 15hp Mercury ( Mariner ) valve clearances ?
Best tip I could give is to get a service manual for your motor. There is a lot more going on with it than just the valve adjustments that you will need to know sooner or later.
The manual is nothing more than another tool in your tool box. The Merc part number is 90-856159R02 Dated SEPTEMBER 2002
Here is a section from it.
Valve Clearance (Cold)
Intake 0.15 - 0.25 mm (0.006 - 0.010 in. )
Exhaust 0.20 - 0.30 mm (0.008 - 0.012 in. )
Perform the following adjustment steps:
Turn the driven gear and align the 1 or X mark on the driven gear with the X mark
on the cylinder block.
Adjust the intake and exhaust valve clearance for cylinder #1.
Turn the driven gear 180° (crank shaft 360°) and align the 2 or X mark on the
driven gear with the X on the cylinder block.
Adjust the intake and exhaust valve clearance for cylinder #2.
Note: In the above instructions, the X is actually a triangular mark on the pulleys shown in the picture.