rectifiers compatable?

[firelitemarine]

will a 4 wire rectifier be able to replace a 3 wire?

if so how can it be done?

also, my tack is messed up and im reading 18+ on the volt meter

thats whats promped me to replace the rect. and i have a 4 wire laying around.

its been doing this since last summer. and i want my tach back, oh crap that rymed, sorry

oh and my engine is a 1989 evinrude 60hp vro (vro disconected long ago)

never had a dead batt, and its been in there since i bought it last june.

 

[Vic.S]

Re: rectifiers compatable?

In theory yes. Just leave one of the yellow wires unconnected. Insulate it though. However the rating of the individual diodes may be lower in the four wire type

Here is a diagram of the four wire type. (the lower diagram of the two)

The three wire type has two fewer diodes. It is a conventional bridge rectifier. The four wire type is the same as a 3 phase bridge rectifier


BUT you'd expect up to 18volts from an unregulated rectifier.

Test your three wire one by following Joe Reeves instructions on testing small rectifiers http://forums.iboats.com/showthread.php?t=190638

It is probably OK

BUT if you use a digital multimeter use the diode test range. They dont necessarily work for diode testing on the ohms ranges

 

[Vic.S]

Re: rectifiers compatable?

continued

Sorry first post was made late last night, after midnight!.


The 18 volts you see indicates that the stator is good and suggests that the rectifier probably is too.

BUT it also indicates that there is probably a bad connection somewhere between the rectifier and the battery. 18 volts is the sort of reading you can get when no battery is connected.

I think your tachometer may not be working for some other reason. Check all the connections to start with.

The tach' itself may be faulty of course

 

[Chris1956]

Re: rectifiers compatable?

The answer to whether a 4 connection rectifier will replace a 3 connection is, it depends what the 3 rectifier is.

Merc uses a standard 4 diode bridge rectifier (normally 4 connections), but internally grounds the -DC connection to the metal case. So the Merc rectifier can be replaced by a 4 connection bridge rectifier, by simply grounding one of the connections.

I am not familar with the Johnnyrude rectifier, but if it is a bridge rectifier, than the answer is yes.

 

[Vic.S]

Re: rectifiers compatable?

I am not familar with the Johnnyrude rectifier

The four wire rectifier is as shown in my diagram. It is identical to a 3 phase full wave bridge rectifier with 3 AC input wires, 6 diodes, a DC positive output wire and a grounded negative.

The three wire type is similar but is just a normal single phase full wave bridge rectifier with 2 AC input wires, 4 diodes, a DC positive output wire and a grounded negative.

Like the Merc rectifier a 3 wire type can be replaced by a suitably rated bridge rectifier in the same way with the negative connection being grounded.

I suspect testing will show that firelitemarine's rectifier is OK.

The fact that his battery charges OK support's that although discounts my suggestion that there is a bad connection between battery and rectifier.