Voltage Problem

Clip your voltmeter's lead on at the battery positive and hit starter.
Get a reading.
if its close to 11 Volts, then yes there is a big drop.
If its 9 Volts, then the battery is the first thing to fix. A good battery should not drop that low during start.
Narrow it down by measuring voltage, or better voltage differences.
For example:
Move the probe to the junction at the relay. Hit the starter and see if the reading is significantly lower than when it was measured on the battery terminal with the starter engaged.
A direct voltage drop measurement is better when looking for drops. One probe on the supply terminal (battery positive), the other terminal on the junction of interest. In this example that's the junction at the relay. Hit the starter. The meter shows the difference in voltage.