2012 Mojo 2.5 Won't Turn Over

[Fastest1]

It sounds like you jumped the starter correctly, There are 2 wires that come into the starter, a hot (big cable) and a signal wire. A screwdriver across those 2 or a wire should spin it.
If not, tap the starter with a hammer, firmly a few times and try again. If that works change the starter as it is going to happen again but it will allow you a short reprieve.
In regards to the relays, that is what I would look into next. Simple to swap around and see if there is a change.
On my boat the relays are on this metal plate on the back of the motor, if you are a v drive they could be on the front maybe.