I apologize, in advance, if this in not appropriate. The vast
experience of this group may offer some advice.

One of my small fleet of boats is powered by a 2001 Suzuki DF70
outboard. Heretofore, a wonderfully reliable engine.

Yesterday, while fishing Chokoloskee, the engine stopped charging -
only 125 hours on the engine. It may not have been charging when I left
the ramp. Dunno, but it cranked just fine. Yes, I will install, at
least, a voltmeter.  Anyway, after a few hours fishing and running live
well the engine barely cranked. New battery, BTW. I put a voltmeter on
the battery while running and it showed 11.4 volts (part of my
toolkit). Of course, I turned off the live well and made sure there
wasn't any other apparent battery drain.

Next fishing hole, the engine wouldn't crank at all. Got it going with
hand start. Didn't want to ruin a good day of fishing! It's not easy
hand starting a 70 four stroke and I wouldn't recommend it as a backup.

About the third fishing hole, had a real hard time getting the engine
going again and if I went to idle for more than a second, it would die.
Voltage was below 11. Time to head to the ramp! Man, I've hand cranked
a few small diesels that were easier to start!

The 30 amp fuse on the starboard side of engine is fine. The "check
engine" light and alarm didn't come on till it was too late.

Regulator? Alternator? I don't even recognize most of the electronics
on this engine. Where should I look for the obvious (inexpensive)
before taking it to the shop computer?

I gotto admit, I miss the simplicity of the small outboards have used
on tenders...that were easy to row.

Thanks!

-fred

Fred wrote:
About the third fishing hole, had a real hard time getting the engine
going again and if I went to idle for more than a second, it would die.
Voltage was below 11.  >>>> snip<<<<
The 30 amp fuse on the starboard side of engine is fine. The "check
engine" light and alarm didn't come on till it was too late.

Regulator? Alternator? I don't even recognize most of the electronics
on this engine. Where should I look for the obvious (inexpensive)
before taking it to the shop computer?

REPLY
Considering most trawlers  also have  some form or dinghy or auxiliary tender
powered by outboards, this is a relevant topic.

Outboard motors of all kinds suffer a common problem.
The engine designers tend to think of the charging circuit as only being used
for the starting battery.
They fail to recognize that many outboard powered boats - especially fishing
machines -  have as much complex electronics and electrical loads as  many
cruiser. Consequently, most outboard engines do not have adequate sized
alternators.
To make matters worse, design configuration tends to perpetuate the original
fly wheel style alternator with a stator ring on the engine block.
This is essentially a refinement of the old flywheel  magneto concept.  While it
may be adequate for recharging the  relatively small energy amount expended to
start the outboard engine,  it fails to provide the power to sustain  live bail
well pumps, echo sounders, possibly radios and even radars not to mention
Koolatron style chest coolers etc.

In the larger engine sizes where a conventional  external alternator is actually
used, they tend to be compact permanent magnet designs much smaller than the
conventional automotive types we are accustomed to on  regular automotive and
boat  propulsion engines.

There are several possibilities as the cause of failure on Fred's boat.

The total combined electrical load may have been enough to drain the battery
because the load current exceeded the charging current.
Engine heat plus ambient temperatures may have caused an intermittent failure in
the alternator/charger coils.

( I once had such a failure where the motor would cut out after getting hot but
every time it was checked  by a mechanic it was cold and thus worked. The point
of failure was worn insulation which shorted out as the coil wires got hot )

Before taking the motor to a service center, recharge the battery fully from an
external source. Restart the engine,  and measure the charging  current going
into the battery. Next  measure the load current, feeding the various electrical
devices on board.
If you have the specifications for the alternator output  you can easily see if
you are overloading the charger circuit.

This is a valid test for any outboard  from a 10 HP once cylinder and up having
electric start.

If this does not reveal  any deficiency then  use a heat gun to heat up the
alternator / flywheel mounted  stator ring  assembly to simulate operating on a
hot summer day.  An infrared thermometer would be useful here.  A weak link in
the electrical system may  reveal itself under temperature stress.

My mechanics training started at age 12  with  fixing  small engines, later on
outboard motors and other magneto driven engines.
I didn't get into diesels until I was nearly 19.

cheers

Arild

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Fred wrote:
About the third fishing hole, had a real hard time getting the engine
going again and if I went to idle for more than a second, it would die.
Voltage was below 11.

REPLY

I forgot to mention that any  alternator  is dependent on speed ( RPM )  for
producing charging current.

When fishing, it is customary to run at slower speeds.  Any alternator  will
produce much less amps at idle or slow trolling speeds than when going flat
out - WOT

So another possibility  for Fred's electrical failure may simply be a function
of prolonged slow speed operation.

This is why  a 3 stage regulator is often a significant improvement  for trawler
boats that do tend to operate a t slower speeds.
Especially true for "express" trawlers that can hit planing speeds but ere often
just  run at displacement speeds to conserve fuel.

A pair of 100 amp alternators on a twin engined trawler may only produce 20 - 30
amps at these slower speeds.
If  the connected load exceeds the charge output you will find the battery
system going dead very often.

Unfortunately the  type of alternator used on most outboards do not lend
themselves to external  regulators.
The very tight  packaging  configuration also precludes installing an after
market  alternator.
These are either too big to fit and in any case, the bearings are designed for a
horizontal shaft  mounting whereas most outboards will only permit a vertical
shaft orientation.  The bearings cannot support a thrust load and the alternator
will fail prematurely  even if you manage to install it.

I have been bugging Balmar to redesign their  100 amp small frame unit  with a
thrust bearing in the back  so as to  allow mounting on big outboards.  So far
no takers.

Arild

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Arild,

Thanks so much for all your expert advice.

This morning, I brought the battery up to 12.5 volts. Two hours on a 10
amp charger. Of course, it cranked right up. Voltage at crank => 12.5
v. Voltage at idle => 12.5 volts. Voltage at fast idle (2000 rpm) =>
12.5 volts.

Engine is actually equipped with a 40 amp alternator. It's been
suggested to me to do stator resistance test followed by
Rectofier/regulator test. Me thinks I need to buy the shop manual to
learn how to do that.

BTW, as soon as I noticed the drain yesterday, I disconnected the
console lead to the battery, which powers all the accessories.  Voltage
at the time was 11.4, which I now learn is just marginal for cranking
this particular engine. I am surprised the so called "check engine"
alarm didn't kick in until the voltage dropped below cranking ability.
Lesson learned. Still, the battery would not charge after running for a
good 30 minutes at almost full throttle.

Thanks again.

-fred