Went to the boat today. Checked the battery connections. Appear tight but I think I'm going to get new cables anyway. They aren't the best cables. Read an older post about the glow plugs. The owner had to push glowplugs for 45 sec, try engine, push glowplugs for 45 sec, try engine, push glowplugs for 45 sec, try engine then it would start. Figured I would give that a try. On my forth try it started right up. The poster ended up replacing the glow plugs which did the trick. I think I'll try that and the solenoid fix and see how I make out.