Problem with rectifier or alternator or other?

[vahunter]

The rectifier was bad on my 79 115hp outboard (tach only zeros w/ ign on and it was not charging) so i replaced it with good one (checked it as Reeves recommends). Hooked it up, started it up, tach went up to about 5000RPM for about 5 seconds and then zeroed back out. Turned motor off, started it back up numerous times and it still only zeros again as before. I checked the rectifier again asper procedure and still checks out good. Would that be a sign for anything? Would my alt. me bad? How would i check that my alt. puting out? Thanks yall,

Buddy

 

[Joe Reeves]

Re: Problem with rectifier or alternator or other?

Are you disconnecting the rectifier wires from the terminal strip before you test the rectifier?

Voltage to the tachometer..... If you're running dual batteries, is it possible that somehow you're throwing 24 volts to that tach? I've never heard of a tachometer failing in that manner.

The 5000 rpms you mention.... was that engine actually running at 5000 rpms, and if so, was this in neutral?

 

[vahunter]

Re: Problem with rectifier or alternator or other?

I did disconnect all 3 wires from the terminal block when i checked it. Its got 12v but the tach only goes to "0" now. The first start up for only 5sec it went up to 5000 that was just the FIRST start up after replacing it. It was probably running 1500 or so. Less than 2000 im pretty sure

 

[vahunter]

Re: Problem with rectifier or alternator or other?

Anyone else have any ideas?

 

[Joe Reeves]

Re: Problem with rectifier or alternator or other?

You state " I checked the rectifier again asper procedure and still checks out good."

Is this the procedure you speak of?

(Small Rectifier Test)
(J. Reeves)

Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.

Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.

Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.

 

[vahunter]

Re: Problem with rectifier or alternator or other?

exactly that

 

[Joe Reeves]

Re: Problem with rectifier or alternator or other?

If that rectifier is good along with the stator, I can only assume that somehow, on one of the wires leading to that tachometer, you have revese polarity being applied to that tachometer.

Checking stator..... Ohm reading between the two disconnected yellow wires..... 6 amp stator = 1.2 ohms +/- .4 ohms.... 10 amp stator = 0.5 ohms +/- 0.2 ohms.

Between either yellow wire and ground, there should be absolutely no reading. Any reading would indicate a short.

 

[aclmvh]

Re: Problem with rectifier or alternator or other?

So it sounds like the new rectifier is fine- motor starting and running, charging system working....so do we have a tachometer problem? Have you checked your current/voltages to the back of the tach?