Seven hours away from a tournament, checking everything as usual to get ready.  Cranking battery showing only partially charged when I tested it.  When I try to turn over the motor or if I hit the trim, it drains the battery completely.  Any advice please? Ground is OK and cables have been cleaned and tightened. 

how old is the battery? and have you tried another?

Two years and no I've not tried another battery yet

You may also need a larger battery. The biggest killer of batteries is discharging too deeply. And the final blow is trying to start an engine on a dead battery, that can kill it in seconds.

A larger battery will have more power remaining at the end of the day for starting an engine and the depth of discharge will not be so deep giving much longer life.

If non-startng battery loads are running it down and being able to start is very important, then you can use a Combiner100 http://www.yandina.com/c100InfoR3.htm between the starting battery and a dedicated "house" battery to keep them separate automatically for discharging but allow both to charge from a single output shore power charger or from the alternator on the motor.

Do you have stuff that is powered all the time like a Lowrance GPS antenna, LSS-1, etc. ?

Have you checked the connections at the battery for corrosion and tightness?

Did you charge the battery after the last use, or did you assume the motor would changer it?