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Replaced rectifier/regulator in the Honda 8

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Voyager
Master Marine Consultant

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USA
5418 Posts

Initially Posted - 02/02/2009 : 22:49:24

At long last, the weather warmed above freezing over the weekend so that I could go out in the garage and work on the trusty Honda 8. Recently, I changed the crankcase oil, changed the gear oil in the bottom unit and cleaned out and replaced the gaskets and O-rings in the carburetor.

Then the coupe-de-gras - I had to tackle replacing the rectifier/regulator. There were about 10 wires, each one had to be pulled out of and re-woven into the neat cable harnesses, and I had to make sure I did not unintentionally disconnect any other cables.

I replaced it, and then the weather took another nosedive. My problem was that I have to run the engine to find out whether the charging circuit works or not. I needed to fill a large bucket up with water to run it. Finally, we got a 40+ degree sunny day, so I went for it.

I hooked up a spare battery, a +/-60A ammeter, my digital voltmeter and connected it up. I connected the gas line, and primed the bulb.

I pressed the starter and after a few coughs and spews, she started. The starter drew about 30A while cranking.

She ran and idled fine, so the carb rebuild apparently worked (although it smelled a little rich).

I checked the ammeter and it read about 5A charging. The real test was the charging voltage, [which in the past had been upwards of 15-16V with a large AC component] read neatly between 13.5 and 14 volts.

NICE! Exactly what I wanted to see.

This summer, in addition to the solar panels, I can use the engine to recharge the battery.

Now -- if only winter would quit so I can get to work rewiring the panel and repainting the bottom. I'm hoping to launch in early April, so there's only about 8 or 9 weeks to go.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - on

islander
Master Marine Consultant

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USA
4025 Posts

Response Posted - 02/03/2009 : 08:43:38

I just did the same thing. My 1997 Honda 9.9 had a 6 amp system that didn't work. I checked with Honda and they don't make the 6 amp charge kit anymore so I got the 10amp as a replacement. The rectifier is a piece of cake,the charging coil involves removing the flywheel. I used a harmonic balancer remover that I had and it worked nicely I haven't tested it yet, but the 10amp will be a nice upgrade.

Edited by - islander on 02/03/2009 08:51:22

Dave Bristle
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Djibouti
10005 Posts

Response Posted - 02/03/2009 : 11:17:09

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Voyager
 ...I checked the ammeter and it read about 5A charging...<hr height="1" noshade id="quote"></blockquote id="quote">Good work, Bruce! Hopefully now it'll work for you like it did for me. I'm curious--was that 5 amps at about idle? The spec for that engine is 12 amps (presumably at peak RPM)... Did you run it up a little, and what did you see?

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Voyager
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Response Posted - 02/03/2009 : 20:03:22

Dave -
I believe the charging current depends on the degree of discharge of the battery, so when I saw that the current was at 5 amps, I didn't get too bothered about it.

My battery was at 12.5 open circuit and the alternator was putting out around 13.5 volts, so this seemed reasonable. I will give it another test on the next warm day, but will make sure to substantially discharge the battery first.

I think I should be able to run the current up to 12 amps.

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Voyager
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5418 Posts

Response Posted - 02/03/2009 : 20:05:30

Scott - sounds like you made a nice upgrade. Let me know how it works out.

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Happy D
Admiral

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921 Posts

Response Posted - 02/04/2009 : 07:51:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">[which in the past had been upwards of 15-16V with a large AC component] <hr height="1" noshade id="quote"></blockquote id="quote">

What does that mean? Where you checking the rectifier output with an AC meter?
Why is this a problem? Does this indicate a faulty rectifier?

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Voyager
Master Marine Consultant

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USA
5418 Posts

Response Posted - 02/04/2009 : 22:35:02

Dan --
Last season, the charging leads were putting out a very high voltage, boiling the battery fluid, and smelling up the cabin with Hydrogen Sulfide (H2S) gas that was quite foul. There was probably a load of raw Hydrogen being generated, so I carefully vented the battery area without generating any sparks.

The measured voltage was approximately 15.5 V DC, then I put a large capacitor in series with the Digital Voltmeter and set the voltmeter to 200 VAC, and found about 40 VAC on the charging circuit.

Somehow, the diodes never fully fried so there was some DC, but some part of the regulator had definitely failed. I got hot DC and very hot AC. It even blew out a 20W incandescent bulb due to overvoltage.

It would charge the battery more or less, but it was quite unsafe. A hot battery, H2S and raw hydrogen. yee-ouch!

There were times when I needed the additional charge while cruising, but I had to rely on the solar panels, and could not depend on such an explosive combination, so I am very glad to have it all sorted out [I hope].

I've got a few more tests to do in the garage, but we should be good to go.

Edited by - on

Happy D
Admiral

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921 Posts

Response Posted - 02/05/2009 : 06:28:08

Voyager,
Thanks for the explanation of that. I never thought of checking for AC through a rectifier to see if it failed.
I learn something new every day.

Edited by - on

Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 02/05/2009 : 13:44:57

Bruce,
I know the last thing you want to do is fool with this thing more but I was wondering if you looked at the AC output of the new rectifier to see if it was clean or still put out some AC? Just for future diagnostic reasoning.

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Voyager
Master Marine Consultant

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USA
5418 Posts

Response Posted - 02/06/2009 : 23:26:30

Simple answer is yes.
All alternators put out pulsating DC which is DC (all above zero volts) but there can be a small time-varying voltage (AC) superimposed on the DC. This is normal for a properly operating circuit. The good news is that the "ripple" voltage helps charging the battery.

The problem I had was that the DC voltage was too hot and boiling the battery fluid, and the AC component was very hot. I could actually hear it over the AM radio - there was a noticeable whine that varied with the speed of the engine.

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Arlyn Stewart
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2980 Posts

Response Posted - 02/07/2009 : 06:18:27

When a diode opens so as to pass AC, it will also cause discharging of the battery into the alternator when not running. If the battery is not being drained dead when left connected to the motor... the diodes in the rectifier should be fine.

The Honda employs voltage regulation, it is not a simple rectifier scheme. Severe over sulfating as you state can be overcharging caused by no regulation but it can also be caused by a battery that is showing inadequate voltage to the regulator. In fact, the battery would be my first suspect because even a fairly new battery can go bad and cause it while an alternator that is not discharging the battery otherwise, is probably fine.

My point is, you said you hooked up to a spare battery and everything looks fine... the test will be when you hook up to the battery that may have been the problem.

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Voyager
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5418 Posts

Response Posted - 02/07/2009 : 09:18:36

Arlyn - excellent point, I plan on doing some work on the boat today, I'll bring the battery home to test it on the new regulator. Thx

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