MC wrote:

I have a two year old Interstate brand marine starting battery.

Snip

It is stored out of the boat in my basement for the
winter and is then connected to a Guest brand trickle charger.

This says it all...:-)

You cannot simply leave a lead acid battery sitting in your basement
uncharged over winter and then expect it to take a full charge using a
trickle charger. You might get away with it for the first year but after
a second year of similar treatment it will be kaput due to sulphation of
the plates. When storing a battery over a lengthy period you need to
have it permanently connected to a maintenance charger which
automatically looks after it so that it is ready to go when you need it.
I recommend chargers from Dual Pro http://www.dualpro.com/
They are rugged, waterproof and use proven technology.

Ross Herbert