I will be helping you today. Most questions will involve troubleshooting, and usually take many posts back and forth. Post back with questions as needed.
I would not say you need a starter just yet. There are a couple of things that would cause that.
1. I know this sounds simple enough, but you are supposed to lubricate teh starter gear shaft once every couple of months with a light spray oil. If the shaft is dry it will not kick up. WD40 works fine for this. I personally use a spray lube make by Evinrude/BRP that I like. It is BRP/OMC 6 in 1 spray oil.
Just a light spray of the starter gear shaft is all you need.
2. Low voltage (voltage drop) to the starter due to bad battery cables or a bad solenoid.
Voltage drop (VD) is a bit difficult to explain here, as it is something that is taught at the college level. But fluke Corp does a good job of explaining it. You can read more about that here;
When you have VD, current that is supposed to go to the starter is being absorbed through resistance in the wires and connections or the solenoid that is not supposed to be there.
The easiest way to confirm VD is to put your volt meter positive lead right on the starters positive lug, negative lead to the battery's negative terminal (has to be the actual battery) and crank the engine over. If you get 9.5 volts or better, voltage is good, and the starter should spin.
If it does not spin, spins slow with that 9.5 volts, or that starter gear does not pop even after lubricated you have a bad starter.
If your voltage is under 9.5, then you have a VD, and you need to find it. Corroded battery cables, loose connections, bad solenoid, and even rotted battery cables is what you're looking for.
Feel free to post back with questions