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Long Beach Marine Electric connects boat owners with licensed, insured marine electricians for marine alternator repair and starter work: alternators that stop charging, voltage regulators that over- or undercharge, belts and wiring faults, and starters that click or crank slowly. On a boat, the alternator is the main charging source underway, so a quiet failure shows up as a dead bank the next time you start up.
What happens on the first visit
- Battery voltage at rest, during cranking and with the engine running. A healthy charging system lifts battery voltage well above resting.
- Voltage-drop test on the alternator output and ground paths, and on the starter cables during cranking.
- Belt tension and condition, plus alternator mounting and connections.
- Regulator and sensing-wire check, including any external regulator and how the charge is split between banks.
- A written finding and a fixed price for repair or replacement.
Not charging with the engine running
When the battery doesn't charge underway, the fault is usually in one of four places: the belt (slipping or broken), the wiring (a corroded output or ground connection, or a blown fuse in the charging path), the regulator (failed or mis-set) or the alternator itself. Measuring voltage at the alternator and at the battery under load separates them quickly. Replacing the alternator first, when a $10 connection was the problem, is the most common wasted spend.
Marine vs automotive alternators and starters
Alternators and starters in engine compartments where gasoline vapor can collect must be ignition-protected, which is the marine requirement covered by SAE J1171 and USCG rules. An automotive replacement may fit the bracket but isn't ignition-protected, which is a fire and explosion risk on gas boats and a survey finding on any boat. Marine units are also built to resist salt-air corrosion.
Alternators and lithium batteries
Lithium banks accept charge so readily that they can hold a standard alternator at full output until it overheats. If you've converted to lithium, or plan to, the alternator usually needs a DC-DC charger or a smart external regulator with temperature sensing. See boat lithium battery conversion.
Insurance, warranty and who pays
Alternator and starter repair is owner-paid. Diagnosis usually takes about an hour at the slip. Rebuilding or replacing a unit depends on the engine, access and part availability, and you get a fixed written price before work starts.
What's included
- Charging-voltage test under load
- Alternator output and ground drop test
- Belt inspection and tensioning
- Regulator and sensing-wire check
- Starter draw and cable drop test
- Ignition-protected replacement units
- Charge splitting between banks
- Lithium-safe charging upgrades
DIY vs cheap fix vs proper charging repair
| Factor | DIY | Cheap operator | Proper marine work |
|---|---|---|---|
| Diagnosis | Buy an alternator | Swap the alternator | Voltage and drop tests first |
| Replacement | Automotive unit | Cheapest fit | Ignition-protected marine unit |
| Wiring | Not checked | Not checked | Output, ground and sensing tested |
| Lithium | Not considered | Not considered | DC-DC or smart regulation |
| Result | Same fault | Fault returns | Charging voltage verified at battery |