Inspect and clean up connectors to solenoids then swap the fwd and rev connectors and see where that gets you (the wrong direction at best). Might help you isolate the problem point.
Double braid might not be the best bet for this application. Three or eight strand would be preferable. If you intend to use the db it will need to fit through the chain link. If it will fit just use a standard eye splice, but it may hang on the gypsy.
I've got 9 years on Lakes Michigan and Huron with a 410DA powered by CAT 3126TA's (385hp). Trying to sell to move to a trawler but I'm sure going to miss the ride, economy and reliability this boat has provided for long distance family cruising where time has been a factor. And very easy...