1988 Johnson Evinrude "CC" 9.9 thru 30 Service Manual, P/N 507660, Page 24Get this manual
Handling LeadAcid Batteries
If spilled or splashed on Any part of Body
Wash with lots of Water Wash And contact Doctor, Fast! Changing Lead Acid Batteries (1) Attach and remove these cables with charger UNPLUGGED from 110 volt wall socket(Prevents shocks if the charger is defective (2) Observe correct polarity when connecting these charger Leads(3) Always charge in well ventilated areaCharging causes acid solution to give off Hydrogen gas thru the Vents in the ca::s. Make sure Vents are openIf clogged, pressure inside may build battery may EXPLODEBattery Gas is Explosive! While Charging or Discharging, remember No Smoking No Flames No Sparks Never remove charger cables off battery posts its sure way to make lots of sparks surrounded by Battery Gas