mestey2004
Seaman Apprentice
- Joined
- Apr 2, 2004
- Messages
- 38
Hi, I am in the final stages of building my boat and I am hooking up the battery cables (ignition off) and it sparks (alot) and then when I go to crank her over it is dead. I check the 90 amp fuse and it is blown. I check all the connections and I find a loose ground on the alternator. Could this cause a short big enough to make the fuse blow? What else could be the problem. I followed the wiring diagrams to the "T". My engine is a 305 1999 with a carborator, thunderbolt iv ignition.<br /><br />thanks for any help!<br /><br />Mike
Automotive norm is to ground through mounts. My boat alternator is very automotive.<br /><br />Is that "ground cable" a large wire attached to a single insulated stud on the back of the alternator? On the Chevrolet alternators I'm familiar with, that is (lately a single wire connection) the charging wire -- other end goes to positive side of circuit. If you were touch or attach its connector to both the case and the stud it would give you the symptoms you cite. Dittos if you had a ground wire incorrectly attached to that terminal in tandem with the charge wire or if the insulator were missing or broken.<br /><br />I'm betting that the culprit is in or around the alternator. Few other wires could short ninety amps without beginning to wither. <br /><br />In the meantime, don't be tempted to short out that that fuse -- since you have capacity for more than 90 amps of short circuit current it would make a hot fire quickly... <br /><br />After checking the alternator connection, I'd isolate every circuit (remove connections or fuses until you can connect bat terminal without ANY sparks. Then reconnect circuits one at a time until you see sizzle at battery post -- that's the bad guy.<br /><br />Of course an ohm meter would work without blowing any fuses...