Start with the basics. Clean all the connections
Use a volt meter to find where the voltage stops.
Being a car mechanic that should have been your first thought
Just an FYI, I had 3 props on board for my 3.0. a 15p for trolling and watersports. A 17p for general boating, an 19p for cruising with 2 people.
No one size prop for small motors
You guys in Australia have go-fast parts for the V6 that we don't get here. If your looking to ship some V6 parts, let me know..... Lol. The V6 will fit my next project better than the V8