1984-1986 Mercury Force 4HP Outboards Service Manual, Page 39Get this manual
TROUBLESHOOTING Poor engine perlormance andor hard starting may be
sig ns of compression problem Specific signs include excessively smoky exhaust, badly fouled plugpower
surging or extreme power lossAll can indicate engine
compression problemsWhen internal damage or wear
Is suspected as the cause of an engine problem8
compression test should be done first