Rectifier already bad?

[MassillonBuckeye]

Re: Rectifier already bad?

Here on iBoats they sell Teleflex which are good. Make sure you get the two stroke model.

Rectifier is indeed good. Maybe that #1 coil not sparking was the reason my tach wasn't working.

The first testing method I posted, which also seems to be the most common one found online, is also flawed. Its results tell me that my good rectifier is BAD. Use the second method I posted.

Recap:Bought boat, tach not working. Rectifier fried. Replaced rectifier, tach works, motor running bad. Tested rectifier as per what looks like Aftermarket service manual, and tests bad(1 week old). Purchased OEM Service manual, rectifier tests good with this method. Also diagnosed bad coil pack and replaced. Tach now works!! but is about 200 RPM off. It doesn't seat on zero but at about 200.
The bum coil was throwing off the tach? I still don't know why the first testing method posted in this thread says my GOOD rectifier is bad.

 

[Sunfish12]

Re: Rectifier already bad?

If your still using the rectifier with the loose terminal, chuck it no matter how it tests. Don't take a chance messing up your stator.

 

[MassillonBuckeye]

Re: Rectifier already bad?

If your still using the rectifier with the loose terminal, chuck it no matter how it tests. Don't take a chance messing up your stator.

Well its not loose. I was able to re-torque without it moving at all. I paid close attention to that part. And if it did slip initially, it was literally a fraction of an inch. I don't know. I was thinking about that. I got a free stator recently on eBay. Actually, 3 coils, stator, brand new switchbox, trigger and bad rectifier for $59. Deal of the century?

 

[oldman570]

Re: Rectifier already bad?

Definatly a good buy even if some of the items are bad. Faira web site states that sometimes the tachs will not return to zero RPMs when turned off but should do so when the switch is turned back on. You need to check to see just how many poles your armature has and set the tach as such. The Faira site tells just what and how to do so. Telflex might have a site also.
Best of Boating, Oldman570

 

[sschefer]

Re: Rectifier already bad?

Just FYI, the tach gets it's signal from the charging coils in the stator not the ignition side of the house. Seems odd when we're used to timing and engine off #1 cylinder but that's the way it is on these outboards. That's why you have the switch on the tach that you set for the number of charging coils (poles) you have on your stator. Some stators have dual pole coils so they can transition from low rpm to high rpm and still produce charging current. In those cases you might set your tach for 12 poles if you had 6 charging coils. 40 amp merc stators are that way. 9 amp Mercs produce low current at idle and 9 amps at higer RPM's. Some of those have 4 poles. It's a crap shoot depending on year and model.

 

[MassillonBuckeye]

Re: Rectifier already bad?

Just FYI, the tach gets it's signal from the charging coils in the stator not the ignition side of the house. Seems odd when we're used to timing and engine off #1 cylinder but that's the way it is on these outboards. That's why you have the switch on the tach that you set for the number of charging coils (poles) you have on your stator. Some stators have dual pole coils so they can transition from low rpm to high rpm and still produce charging current. In those cases you might set your tach for 12 poles if you had 6 charging coils. 40 amp merc stators are that way. 9 amp Mercs produce low current at idle and 9 amps at higer RPM's. Some of those have 4 poles. It's a crap shoot depending on year and model.

The tach does operate properly. It just doesn't sit on Zero anymore. So it starts out at 200 RPM. 200 RPM is my Zero. I wonder if I can just move the whole apparatus inside slightly to make the needle move toward the peg. Hmm.

Yeah, this is one of the 7~9 amp stators. Not sure how many charging coils. I thought I read something about 12 poles setting for these 3cyl 70Hp Mercs, but not sure as mine was already set. And no numbers on the back which I can see. I have a spare stator. Can I just count them?

 

[j_martin]

Re: Rectifier already bad?

You can hook your tach up to either of the yellow wires from the stator and after setting the pole filter on it, with the engine running, it should give you correct readings. If it doesn't, your tach is faulty. No need to make it difficult.

1. Remove the Battery + wire from the rectifier.
2. Take a simple 12v light bulb type tester and connect one side to ground and the other side to the pole on the rectifier that is marked Bat + or where the manual says the Bat + is supposed to be connected. Start the engine and if the light bulb lights steady then the rectifier is probably just fine.

Don't ever run a rectifier without a battery load on it unless it's one of the high voltage rectifiers we suggest you put in (35A 200v bridge rectifier). This test will at minimum probably blow the test light, and if the engine is revved will probably exceed the rectifier's reverse voltage rating and short it out.

You can test the stator by disconnecting the yellow wires, and measuring the AC voltage between them. It should be about 15V per 1000 rpm of engine speed. It'll either be about right, or way low/missing.

 

[MassillonBuckeye]

Re: Rectifier already bad?

Don't ever run a rectifier without a battery load on it unless it's one of the high voltage rectifiers we suggest you put in (35A 200v bridge rectifier). This test will at minimum probably blow the test light, and if the engine is revved will probably exceed the rectifier's reverse voltage rating and short it out.

You can test the stator by disconnecting the yellow wires, and measuring the AC voltage between them. It should be about 15V per 1000 rpm of engine speed. It'll either be about right, or way low/missing.

Good info. Only testing I had done on the stator was resistances which tested OK. I do have DVA adapter ready if I needed. Maybe I'll do this simple test between the yellows. That or checking the voltage at the battery while underway should tell me if its charging also?

 

[j_martin]

Re: Rectifier already bad?

Didn't see your other question. Yes, you can just count them. (probably 12) They are evenly spaced, and some might be potted differently. count them also.

Not 0 on the tachometer is an internal problem, maybe just an adjustment.

If you put a DC voltmeter on the battery. It should read 12 and change before start. With the engine running, on muffs is OK, it should climb a bit when the engine is running. If it just sits there like it was before the start, you have a problem.

Yer stator is probably OK. The only way they can ohm good and be bad is with a single shorted turn, and that is usually smokey, and will usually also cause ignition troubles.