Didn't get any help in rec.boats.electronics.
Perhaps someone has an idea here......

Had some more time to mess with this today.
Here's an update on the symptoms.

Gas genset, 7Kw Westerbeke 1998. Looks like the carb has probably been
off (no red paint). Other than that, no visibile repairs/replacements.

To start this unit, you push a button that instead of preheat like on a
diesel unit, it bypasses the low oil shutdown, it runs the fuel lift
pump, and
energizes a choke solenoid that closes the butterfly in the carb.

What I first found was that the unit would bog down in RPM (like
starving for fuel, running down, and recovering right before it
stumbles) unless the choke butterfly was physically held in the closed
position.
After a while, the unit stopped wandering, and settled in to it's 1800
RPM. (I guess. sounds right, but no measurement)

So, let's call that one problem, but here's the real one:

The output voltage, however is around only 100 volts AC, and may vary
between 95 and 105 volts, LOAD or NO LOAD. Something tells me that's key.

Running appliances like the air conditioners will only be successful
for a few minutes. Then the Cruiseairs shut down, with a LO AC error
message on their displays. On shorepower, they run all day, no
problem.

I pulled the full wave bridge rectifier, and checked it with a meter
in the diode mode.
It appears to be intact. I did notice some corrosion from one leg to
the case. Hoping that was it, I cleaned it thoroughly, but no deal.
Still at 100 v max. MAYBE this is breaking down when voltage is
applied, but I doubt it.

What's the next thing you would look at? I'm thinking an electrical
problem now. How would one check things like the windings and the
diodes?

"C. Sadler" wrote in message
om...


After a while, the unit stopped wandering, and settled in to it's 1800
RPM. (I guess. sounds right, but no measurement)

Don't guess, measure it!

If the RPM is low, your voltage will be low as well.

Do NOT, however, attempt to make up for low voltage by cranking up the RPM.
The 60 cycles/second that you need is directly a function of 1800 RPM.



So, let's call that one problem, but here's the real one:

The output voltage, however is around only 100 volts AC, and may vary
between 95 and 105 volts, LOAD or NO LOAD. Something tells me that's
key.

As I mentioned above, if the RPM isn't right, all other measurements are
pointless.

I pulled the full wave bridge rectifier, and checked it with a meter
in the diode mode.

The rectifier would probably be for creating a DC voltage that the ignition
and fuel pump circuits would need, I doubt that it would be involved with
the generation of the AC power.


What's the next thing you would look at? I'm thinking an electrical
problem now. How would one check things like the windings and the
diodes?

I would check the brushes.

Rod McInnis

In article ,
"Rod McInnis" wrote:

"C. Sadler" wrote in message
om...


After a while, the unit stopped wandering, and settled in to it's 1800
RPM. (I guess. sounds right, but no measurement)


The rectifier would probably be for creating a DC voltage that the ignition
and fuel pump circuits would need, I doubt that it would be involved with
the generation of the AC power.


What's the next thing you would look at? I'm thinking an electrical
problem now. How would one check things like the windings and the
diodes?

I would check the brushes.

Rod McInnis




Wrong answer. The Rectifier in the generator is used to produce the
DC Field Current on the sator of the genset. These diodes are built
into the sator on a Brushless, and on the frame in a Brushed. Bad
Rectifier, equals no field current = No output voltage. Usually
this type of system is selfregulating or nonregulating, and as a rule
is used on cheaper type gensets. The winding turns ratio, and field
current set the voltage, and the rpm set the frequency. A more expensive
and better system uses an AVR to sense the output voltage and adjusts
the Field Current, in a "Closed Loop Control System, with the cycles
again controlled by the rpm. If the rpm = 1800 or 3600 as the case
maybe, and the output voltage is still under 110Vac then I would suspect
that you have shorted turns in either the sator or Main windings.

Bruce in alaska The Generator King of Excursion Inlet.....
--
add a 2 before @

Thanks guys.

Westerbeke would take issue with the "cheaper unit" (so would my
wallet), but I'm sure it's all relative.

I was surprised to not find an electronic voltage regulator.

I will check the frequency this weekend as a first step.

What I do know is that it used to do this right before I bought the
boat. A gen mechanic did something that fixed it, we completed the
sale, and now 4 months later it's doing it again. Now, if I can just
find that mechanic.

Thanks guys.

Westerbeke would take issue with the "cheaper unit" (so would my
wallet), but I'm sure it's all relative.

I was surprised to not find an electronic voltage regulator.

I will check the frequency this weekend as a first step.

What I do know is that it used to do this right before I bought the
boat. A gen mechanic did something that fixed it, we completed the
sale, and now 4 months later it's doing it again. Now, if I can just
find that mechanic.