I have the same engine, yes it does have an alternator, and I use a PWC
(motorcycle style) battery. Works very well.
Jim
John Wentworth wrote:

Your Johnson has an alternator that should keep the battery charged in
normal use. A regular battery will work just fine, the deep cycles are
designed for use with an electric trolling motor.

"GWSears" wrote in message
om...

Hi,
I recently bought a 1998 2 stroke electric start 25 hp Johnson. I do
not know if it has an alternator or if I have to charge the battery
after use like an electric motor. I have not used it yet, only started
it. Someone please help me with this lame question :-) Oh and one
more. Should I use a deep cycle battery or will a regular auto battery
work just as well?
Thanks,
GeoW