Have you looked at brass compression fittings?
Also, Zurn fittings are fairly easy install.
I'm not able to picture exactly what you're trying to do, but compression fittings will usually result in leak-free connection.
You generally need to go to an actual plumbing supply store to get the less-common connectors that the big stores don't carry.
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine