There are a whole raft of coupling errors that will cause vibration problems. If you have encountered any interesting ones please post them below. I suggest retitling the subject field to reflect the type of coupling. Here goes the first one.
Marine lube is refers to the style of lubrication.
A marine lube coupling is a spacer type gear coupling with an oil spray bar directing oil into gear mesh at both ends of the spacer. The coupling in enclosed with an oil drain in the bottom of the coupling and oil exit holes drilled in the hubs to alow the oil to flow through the teeth. A common problem with these couplings is loss of spacer centering register. Some couplings have barreled and crowned teeth that mesh with straight cut teeth. The crown should have a slight clearance fit so that the spacer will remain centered while rotating and remain balanced.