Fire It Up (Electricity)
An engine’s DC electrical system is another common point of issue, but usually the least threatening. That is, if the electrical system shuts down the engine won’t overheat; it just won’t start or run. On the other hand, if it won’t start and you’re stuck adrift or at anchor 100 miles from the nearest port, that’s kind of a big deal.
“Loose or dirty connections are a huge problem in DC systems,” Berlin says, “but nobody ever checks them either.”
The cable from the battery to the starter motor is critical, so check those connections first. Also check the wires to the oil pressure switch, the cooling water temperature switch and the battery switch. ...Any wire involved in monitoring the engine needs to be monitored by you.
Fuses are also culprits. Also check the starter motor for a bad solenoid or a bad Bendix drive.
Berlin points to the alternator as another source of concern. “A guy called because his batteries weren’t charging,” Berlin says. “And it turned out his alternator had worked loose from his engine.”
Check that the bolts holding the alternator in place are properly torqued. Equally important, check that the belts are both the right size and type for your engine and also that they are tightened. This goes for all the belts on the engine, which can cause the engine to overheat if they’re too loose. When changing belts, a simple belt-tension jack ($20, mscdirect.com) set between the pulleys can make sure they’re tight.