1988-1992 Mercury Force 5HP Outboards Service Manual, Page 90Get this manual
4 Remove spark plug from power headCrank over power head
OBSERVE
Weak, yellowish or red spark, or no spark at all
POSSIBLE CAUSE
Poor groundsDamaged or worn high tension leadMalfunctioning stop switchPoints not adjusted properly, too wide or too narrowPoints pitted or burnedPoorly grounded or defective top crankshaft seal