Honda BF50 Rectifier Replacement

[Tsatzsue]

Hi All,

So, I ordered an aftermarket regulator since there seem to be no OEM rectifiers available. Wires matched up and all looked great. Voltages were good and at about 14V from the 17 that I would get under 3/4 throttle. However the tach would drop in and out and flutter. I checked the wiring and nothing. I tied the old one back in and it worked fine. I returned it and have ordered another, different one with good reviews. Any suggestions. I really don't want to cook my batteries.
KB

[opie]

Your new rectifier/regulator will cut out the charging function when rpms get high enough to exceed a certain amount of amps. The circuitry in your replacement device is not as sophisticated as the oem device which had a non-drop-off lead available for the tach. Therefore, your tach output will drop when your battery voltage output drops by the cheap non-oem rectifier/regulator.

I have a thread below from 2010 which explains it and the fix.

Basically, I just moved the tach gray wire off of the charge coil pair of wires and reconnected that gray wire to the exciter coil pair. (The charge coil and the exciter coil both are under the flywheel, so therefore the rpms are identical.)

Link to 2010 thread here.
https://www.macgregorsailors.com/forum ... 186052

The picture shows my new tap into the exciter coil circuit.

[opie]

Ps-
I thought I would explain the picture above of my wiring kluge.

There are three wire nuts involved whereas anyone will see only two are needed.

I cut the wire too short at the top and had to add another piece. Ha.



I must warn you that the third connector down from the top is my “gray” tach wire which I unplugged from its charge connection and substituted the tap-in to the exciter connection. The warning is that my engine is 1999 model. Please! Look at your own wiring diagram to make sure where your “gray “ wire connection is. It could be higher or lower in the CDI stack of plugs. Plus, my engine has a CDI ignition. If yours is ECM, things may differ.

But, all in all, the tach is looking for a rapidly occillilating ac signal. Both the charge coil and the exciter coil produce such a signal. It is just that the exciter coil output does not go to the rectifier/regulator.

It has worked fine for 15 years…..

[opie]

Here is one correction that needs to be made. I have been under a misconception about nomenclature of outboard engines (probably all small engines) regarding the word “stator.”

I researched the word “stator” and find out that the stator term refers to all coils under the flywheel. Some engines’ stator assembly includes both the exciter and the charge coils in one assembly. The Honda 50 hp engine stator coil assembly includes a separate charge coil (sometimes 2 charge coils in parallel if 10 amp and 1 charge coil if 5 amp) and a separate exciter coil. In addition, under the Honda 50 hp cam pulley is the pulser coil. Then you have the three ignition coils for the spark plugs. Because of my error I am going to edit my submissions above to change all references to “stator/charge” coil to “charge coil” only.

[adudinsk]

Yes the after market rectifiers are basic,... often just a bridge rectifier...and some VERY simple circuitry. This often leads to poor Tach readings.
They work for charging.. but... you will have this issue.

Try to find an original Honda unit on EBAY if the tack is that much of a problem

[Tsatzsue]

Thanks Opie. I did read your post. A few times actually before you wrote me. I was hoping to just find an OEM replacement. I might have found one. It won't be due in for this weekend so I put the cheap one back in. My daughter flipped the Perko selector to off while under full headway speed. Took out stereo too. It would seem that if they are discontinued someone would come up with an exact replacement. Trial and error right now. I may go for your method. My motor is a 2005 but looks the same. Thank you for responding. This is a great source of all things Macgregor.

[Be Free]

That is why I have a dedicated start battery wired straight to the engine. I was so worried about blowing the rectifier that I would not even switch batteries on a make-before-break selector switch while the engine was running.

Now that only the house batteries are connected to the Perko I sometimes turn it on and off while the engine is running just for the fun of it*.




*Not really, but I could!