Also use nuts and washers on your cables...not the little hand tight wing nuts. I know that doesn't sound like it would make a difference but it will. Think if you just "hand tighten" your lugs on your vehicle....lawn mower....or 4 wheeler...same goes for the boat. They need to be tight.
Try pouring a little coke on the posts...this will eat away any corrosion and will give you a better connection for a bit while wet. Pour then try to start and see if that changes anything...if so...check your connections.
Just like IBFSHN said...check those wires. Saw this on a kenworth a couple weeks ago. Changed everything out...still problems. Cut up into the cable about 6"...corroded the whole way. Redid that piece...now we are all good.
"But if serving the Lord seems undesirable to you, then choose for yourselves this day whom you will serve, whether the gods your ancestors served beyond the Euphrates, or the gods of the Amorites, in whose land you are living. But as for me and my household, we will serve the Lord.” Joshua 25:15