1972 65 hp Rectifier

[UncleBuck81]

I have a question. I read out my rectifier in accordance with the manual and it failed, read it like 10 times to be sure. My question is will this cause the motor not to start or will it only just not charge the battery??? ANy help is greatly appreciated as lake season is approaching.


Buck

 

[Joe Reeves]

Re: 1972 65 hp Rectifier

The rectifer affects only the charging system. It has nothing to do with the ignition or starting system.

 

[jay_merrill]

Re: 1972 65 hp Rectifier

Along with the shift diode, it also supplies the voltage needed to hold the gearcase in neutral. I've never tried to start a hydro-electric shift motor with a defective rectifier, but I suppose it is possible that the prop may spin, even when the shift handle is in neutral. Then again, it may not because the battery may supply the power needed too.

 

[F_R]

Re: 1972 65 hp Rectifier

The ignition switch supplies voltage to the shift while starting so it will be in neutral. The shift diodes are to prevent it from instantly slamming into forward when you turn the key to off. In that situation, the alternator/diodes supplies the shift voltage until the shaft stops rotating.

 

[wavrider]

Re: 1972 65 hp Rectifier

YES a rectifier will not have anything to do with an ignition system.

UNLESS it is shorted diodes and alternating current is going to ground, then it will be on every component in your ignition system.

trouble shooting matrix even instructs the technician to disconnect the rectifier and see if there is spark, first step in troubleshooting an ignition system.

try disconnecting the rectifier, the two yellow input wires when disconnected will totally take your rectifier out of the circuit

http://www.boatpartstore.com/tips.asp

follow the link to your engine and use troubleshooting matrix to help find the problem.

 

[F_R]

Re: 1972 65 hp Rectifier

What is the rational for thinking that the alternating current is going to ground? It would be the alternating current meant for charging the battery that goes to ground. There are separate coils on the stator for generating the 300 volt AC going to the power pack. Outside of being on the same stator, the two systems are completely isolated from each other and electrically unrelated.

 

[jay_merrill]

Re: 1972 65 hp Rectifier

I think FR is corrrect. The stator on a 1972 Johnson 65hp has four wires coming from it. Two go to the #4 & #5 positions on the powerpack and the other two go to the rectifier/charge circuit.

Here's the schematic:

 

[wavrider]

Re: 1972 65 hp Rectifier

YEs it is isolated, until youput the DC ground into the circuit that connects to the battery.

as long as the diodes are in working order no AC will enter the circuit

if the diodes short, the AC sine wave can and will ride on the DC voltage

look at your typical battery charger, the only side rectified is the negative side, the positive side is actually AC stepped down by the transformer and this is used to charge the battery.

take your o-scope and look at the signal, it will be a ac sine wave on the positive side.

this is fine for charging battery, but not good for amp ignitions.

I could hunt the posts but spent over a week helpng someone trouble shoot his ignition system on this forum, he replaced practically everything in the system andstill had intermiottent problems, he finally installed new rectifier and fixed the problem, it had one leg of the negative side of the bridge shorted and alowing AC to go to ground causing all types of weird problems.

In some RF circuits for amplifiers use the same conductors for AC and DC, just use a blocking cap or doorknob cap in series to block the DC and allow AC to pas into the circuit.

FR remember the tube theory, and lighting filiments with AC voltage and the bias and B+ circuits are DC, had to ground the grid with RF chokes and bypass caps to keep the AC from entering?

Same principal applies to the charging system of the outboard.

If that rectifier shorts on the positive side, no worries, it will charge the battery, but make your tach act wierd in display

if it shorts on the negative bridge, then it has a problem because it will go to the ground in the battery and it is connected to the block ground on the engine, as well as the amplifier ground.

Jay thanks for the schematic.

 

[wavrider]

Re: 1972 65 hp Rectifier

YEs it is isolated, until youput the DC ground into the circuit that connects to the battery.

as long as the diodes are in working order no AC will enter the circuit

if the diodes short, the AC sine wave can and will ride on the DC voltage

look at your typical battery charger, the only side rectified is the negative side, the positive side is actually AC stepped down by the transformer and this is used to charge the battery.

take your o-scope and look at the signal, it will be a ac sine wave on the positive side.

this is fine for charging battery, but not good for amp ignitions.

I could hunt the posts but spent over a week helpng someone trouble shoot his ignition system on this forum, he replaced practically everything in the system andstill had intermiottent problems, he finally installed new rectifier and fixed the problem, it had one leg of the negative side of the bridge shorted and alowing AC to go to ground causing all types of weird problems.

In some RF circuits for amplifiers use the same conductors for AC and DC, just use a blocking cap or doorknob cap in series to block the DC and allow AC to pas into the circuit.

FR remember the tube theory, and lighting filiments with AC voltage and the bias and B+ circuits are DC, had to ground the grid with RF chokes and bypass caps to keep the AC from entering?

Same principal applies to the charging system of the outboard.

If that rectifier shorts on the positive side, no worries, it will charge the battery, but make your tach act wierd in display

if it shorts on the negative bridge, then it has a problem because it will go to the ground in the battery and it is connected to the block ground on the engine, as well as the amplifier ground.

Jay thanks for the schematic.

http://forums.iboats.com/showthread.php?t=235258&highlight=wavrider

refer to this post, wormz had the engine that shows exactly what I am trying to describe,, thaks guys now I got some boots to replace in a mercruiser outdrive

 

[Joe Reeves]

Re: 1972 65 hp Rectifier

...

 

[wavrider]

Re: 1972 65 hp Rectifier

how did it get two posts?

anyway the good thing is the gentleman found a faulty ignition switch or wiring so hopefully he got it figured out.

wished changing the boots on that mercruiser outdrive was as easy as finding ignition problems

 

[F_R]

Re: 1972 65 hp Rectifier

Wavrider, I will respectfully try to figure out what in blazes you just said.

 

[HighTrim]

Re: 1972 65 hp Rectifier

FR remember the tube theory, and lighting filiments with AC voltage and the bias and B+ circuits are DC, had to ground the grid with RF chokes and bypass caps to keep the AC from entering?

Wavrider, I will respectfully try to figure out what in blazes you just said.

I was just trying to figure THAT out, LOL. Much too advanced for me. I am going to assume that Wav is referring to televisions??

 

[F_R]

Re: 1972 65 hp Rectifier

Don't even try to figure that out. It has nothing to do with outboards. The battery charge circuit and ignition supply circuit are completely independent and not connected in any way. To say that one affects the other would be like saying my neighbor's house burned down because my water heater had a short circuit.

 

[wavrider]

Re: 1972 65 hp Rectifier

Don't even try to figure that out. It has nothing to do with outboards. The battery charge circuit and ignition supply circuit are completely independent and not connected in any way. To say that one affects the other would be like saying my neighbor's house burned down because my water heater had a short circuit.

So the amplifier ground on the "ignition system" has a different ground than the charging system?

How many ground systems do you have on your boat?

On all of mine and any I have ever assisted on there was only one ground for everything.

If I take the multimeter, switch it to the OHM settings, place one lead on the ground terminal of the amplifier, the other lead on the block of the engine it should read 0 ohms, a short correct?

So if I place the same lead on the negative side of the battery with the cable connected to the engine, i should still read a short correct?

So the only thing commen in the ignition system and the charging system is the ground circuit, if it is not commen why is it always advised to clean all the ground contacts that the ignition system attaches to? If it is a seperate system why bother cleaning them?

 

[F_R]

Re: 1972 65 hp Rectifier

The motor in question does not even have an amplifier. It is Mag CD and has a power pack. I can't talk to you on this subject. Enjoy your day.

 

[wavrider]

Re: 1972 65 hp Rectifier

, going down to the lake bass fishing, thanks Fr for the info and you have assisted me so many times in troubleshooting many different problems on outboards. Your knowledge and expertise is unsurpassable.

This is just a hobby to me, I purchase old broke outboards and basically give them away to friends, lucky if I get back what I have put into them, but it does give me and my teenage son some projects to do. Thanks, and as always have enjoyed the conversation, no ego here at all, just enjoy hearing another point of view on different subjects, good day

 

[Joe Reeves]

Re: 1972 65 hp Rectifier

Uncle Buck..... Still there?

 

[wavrider]

Re: 1972 65 hp Rectifier

Joe, I think he found his problem in the ignition switch, disconnected the kill wire and it had spark, another thread

 

[UncleBuck81]

Re: 1972 65 hp Rectifier

I found the problem, It was the ign switch, disconnect the b/y from #6 and get a strong blue spark. Re-connect....nothing. I did replace the rectifier though, as it read bad iaw the book and when I flipped it over upon removing it the hard sealant in the rectifier was cracked and some wiring was almost exposed. Thanks for all your help.



Buck