It is my understanding that a battery needs "exercised". Long periods
of non-usage (over the fall/winter/spring months) will result in the
battery loosing its charge and not be able to accept a charge.

With that said, is it possible that if I wired my battery (in
parallel) to my Ford truck battery, will it be "exercised" and be
ready for another full year of boating, or will it damage the PWC
battery?

I'm trying to avoid the cost of trading in the old battery and
purchasing a new battery each summer.

Thanks in advanced,

Dizouglas