I have a 1978 Mercruiser 470. Like many of the 470s, this one had charging system problems and a couple of weeks ago it died on the lake. To make a long story short, the regulator was blown. I performed a ground continuity test on the positive terminals of the regulator and discovered that at least one of the diodes was bad. (The regulator also heated up while I was recharging the battery.) After checking the prices on replacements I did what any reasonable person would do and ordered a bracket and single wire alternator to replace the old system. The mechanics of the replacement were fairly simple, but the wiring has proven to be a nightmare. After disconnecting the battery, here's what I did.
1--I removed the old yellow stator wires from the regulator, insulated and secured them.
2--I removed the other two wires from the regulator, one red/white and one solid red jumper. The old regulator is still there, but it has no wires attached to it. The jumper was only 6-8 inches long and connected to the battery side of the solenoid. I completely removed the jumper from the system.
3--Using a meter, I did a continuity check and determined that the red/white wire from the old regulator (10 or 12 gauge) was connected to the positive side of my ammeter. A solid red wire (also 10-12 gauge) runs from the other side of the ammeter through the main circuit breaker, and back to the battery side of the solenoid.
4--I attached the positive cable of the new single wire alternator to the red/white wire and grounded the new alternator to the engine. This is the set up described in the directions that came with the new kit. This is also the set up diagrammed in my manual for a single wire alternator.
5--I did a continuity check and confirmed that the alternator was not grounded, nor was the battery side of the solenoid. The alternator does have continuity back to the positive battery cable.
6--I reattached the battery cables and turned the key to the "On" (not start) position. Nothing happed. I turned the key off and flipped the horn switch just to see what would happen, and the instruments went haywire. By that I mean that they seemed to read backwards. When I let go of the horn everything returned to dead.
7--I rechecked all of my attachments, unhooked the new alternator (positive cable and ground), and checked everything again. Same result.
8--I bumped the starter just to see what would happen. I let it turn over for less than a second.
9--Disassembled and reassembled everything.
10--Found that somewhere in the process I had burned out the fused assembly on the battery side of the solenoid, probably when I bumped the starter.
I'll get a new fuse assembly on Wednesday, but I don't think that will solve the problem and I hate to reconnect it until I have some idea of why it burned out and why the instruments are haywire.
I'm sorry for the long post, but if you have any suggestions please help. I've reached the end of what I know to to and my wife is beginning to give me sour looks every time I come in from the garage.
1--I removed the old yellow stator wires from the regulator, insulated and secured them.
2--I removed the other two wires from the regulator, one red/white and one solid red jumper. The old regulator is still there, but it has no wires attached to it. The jumper was only 6-8 inches long and connected to the battery side of the solenoid. I completely removed the jumper from the system.
3--Using a meter, I did a continuity check and determined that the red/white wire from the old regulator (10 or 12 gauge) was connected to the positive side of my ammeter. A solid red wire (also 10-12 gauge) runs from the other side of the ammeter through the main circuit breaker, and back to the battery side of the solenoid.
4--I attached the positive cable of the new single wire alternator to the red/white wire and grounded the new alternator to the engine. This is the set up described in the directions that came with the new kit. This is also the set up diagrammed in my manual for a single wire alternator.
5--I did a continuity check and confirmed that the alternator was not grounded, nor was the battery side of the solenoid. The alternator does have continuity back to the positive battery cable.
6--I reattached the battery cables and turned the key to the "On" (not start) position. Nothing happed. I turned the key off and flipped the horn switch just to see what would happen, and the instruments went haywire. By that I mean that they seemed to read backwards. When I let go of the horn everything returned to dead.
7--I rechecked all of my attachments, unhooked the new alternator (positive cable and ground), and checked everything again. Same result.
8--I bumped the starter just to see what would happen. I let it turn over for less than a second.
9--Disassembled and reassembled everything.
10--Found that somewhere in the process I had burned out the fused assembly on the battery side of the solenoid, probably when I bumped the starter.
I'll get a new fuse assembly on Wednesday, but I don't think that will solve the problem and I hate to reconnect it until I have some idea of why it burned out and why the instruments are haywire.
I'm sorry for the long post, but if you have any suggestions please help. I've reached the end of what I know to to and my wife is beginning to give me sour looks every time I come in from the garage.
