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Kohler 8KW marine unit-unique symptom

Richland

Registered
Responded to a customer who related a problem that's existed for 2 years, although he didn't have time to have the problem diagnosed when symptoms were first observed. A Kohler KW marine generator, model 8E, serial # 0714783, spec: GM 17772, a 1999 or 2000 model with 730 hours on the clock, gasoline powered. The primary symptom consists of the following observations: Unit starts and runs well, has been relatively well maintained; and the controller consists of 3 separate circuit boards, all have been replaced by the owner. He possesses enough knowledge to disconnect the battery, mark wiring,ect prior to board replacement, takes photos as well as writing notes prior to taking action. The voltage regulator [4th board] has also been replaced with an identical new OEM unit. The majority of the boat went underwater for 6 hours, including the generator. Once the boat was raised, the generator was subject to some high powered blow dryers in an attempt dry out the internal components. The unit was never disassembled, although the carb was cleaned and reassembled, motor was drained and refilled with oil, plugs an ignition coil replaced,all in a time frame of 6-8 hours after boat was drained, based on his description of events.
When the generator is started, it runs like new, very stable RPM's immediately and after running 20 minutes or so, the unit exhibits no abnormal operation, the output voltage measures 246 VAC, line to line; and 122 VAC line to ground on each phase. Frequency output measures 60 Hz, no alarms sound off nor any engine/generator abnormality responds that I can detect, via observation or measurement. All wiring terminals are tight and clean externally. Transfer takes place via interlocking circuit breakers and they function correctly, these breakers were not subject to immersion which took place a little over 2 years ago. However, when the unit is placed under any load, small or significant, the resulting voltages drop immediately to 40 VAC, or maybe 2-3 volts; and sometimes the voltage increases to 245 VAC, the frequency always remains in the 61-62 Hz range, regardless of voltage drop or increase. These results are the same on both phases, the procedure I used was to test only one load at a time to eliminate back-feeding from a malfunctioning device,appliance,ect. Immediately after turning a single load circuit breaker off, the voltage values immediately return to normal while I measure the VAC output leads of the genny. Have not measured resistance values of rotor or stator windings; have not measured resistance values to ground. Generator frame measures no voltage on it referenced to a separate isolated grounding point. Obviously, something internally has malfunctioned, if anyone can provide some insight, I would be most appreciative. Unit is located in a very tight location, if generator has to be totally disassembled, a good portion of the deck floor will have to be removed for accessibility. Any help would be sincerely appreciated from resident experts. Have never observed this unique symptom, though it appears to be related to the byproduct of water immersion. Many Thanks! :shrug:

separate, isolated grounding point
 

len k

Subscriber
Last Subscription Date
12/12/2018
IF it was salt water might consider washing salt off windings and connectors with freash water to eliminate potential future corrosion. Then baking maybe 120 deg for ~ a day to dry it out.

I haven't looked at Koler's design much. Just a guess, a connector has corroded and is making high resistance, maybe in 120 output circuit. Reasonable to assume boat dried slowly and had very high humidity for weeks after sinking. Might check for voltage right at winding 120VAC leads. On Onan Emerald gens 2VAC at no-load is typical of no feild current, just residual magnetism from laminations.
 
Last edited:

John Newman Jr.

Subscriber
Age
64
Last Subscription Date
01/10/2019
Corrosion on the slip rings allowing you to measure full voltage with no load, but enough resistance that prevents powering a load???:shrug:
 

pegasuspinto

Registered
I'd check to make sure the VR is getting correct voltage (Same as the output). SHould see 120vac between 33 and 44, and i assume the same between 33 and 55. 33-44 is sensing and 33-55 powers the AVR. Also measure the DC out to the slip rings, the amps should increase with the voltage as the load increases.

Megger ALL the windings.
 

len k

Subscriber
Last Subscription Date
12/12/2018
Good point on cleaning slip rings , on an Onan NHE that can kill the $$ voltage reg.

On a NHE that likely will result in mildly lower 120V output under load, something like ~30V drop at ~40% rated load, but Kohler may be a different design.
 

Richland

Registered
Thanks Gentlemen, All suggestions appreciated. Yes, need to check all resistance values with a meter, then test insulation for low resistance to ground. As mentioned, voltage regulator is brand new, replaced last week. All voltages and frequency are normal with no load. Unit was drained and dried shortly after being submersed, maybe some residual flaking from other metals ended up somewhere inside. Another question is: Did Kohler use a bridge rectifier in conjunction with the field circuit? Have been searching for a 8 Kw service manual and/or schematic for marine units and have not found one as of yet. Corrosion on the brush terminals is a distinct possibility. If the field lacks sufficient current, would the VAC output from the stator be affected in the manner described?
 

len k

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Last Subscription Date
12/12/2018
Don't know about Kolher, but in a Onan NHM (NHE) when I tested it, without the AC voltage reg connected, by putting a fixed DC voltage to the rotating feild (thru the brushes) the field current does not vary with AC load. The 120V output did drop in voltage by ~ 30V with a 40% of gen rated load. This drop seems to be alot less than what you say you are seeing.

But during normal operation with the AC voltage reg installed, the reg will increase voltage to the field, and therefore feild current, as you add a load to the 120V output. It does this to prevent the 120V output voltage from dropping

Onan NHM has a performance test where you remove the AC voltage reg and apply 12VDC to the field and measure voltage on output windings. Maybe Kohler has a similar preformance test.
 

LWB250

Registered
is the engine loading up when this happens
What he said.

If the engine is showing no indications of a load, you've got winding problems.

If the boat went into salt water, I would be willing to bet the insulation is toast. Only way to really determine that is to put a merger (megohm meter) to it.

Even if it was fresh water, to be in the drink that long pretty much guarantees that moisture got all the way into the windings, and no amount of time with high powered blowers is going to fix that. Only way to do that is to take the alternator off the engine and bake it.

Dan
 

Richland

Registered
Many thanks Dan, as you and others have correctly surmised, the engine exhibits no loading of any kind and I failed to mention that no device becomes powered or can be turned on and operate when a single circuit breaker is turned on. When I leave a breaker on to supply some lights or other small loads, even with a voltage value of 40 volts on one phase and 240 volts on the other phase, no alarms are triggered of any kind. regardless of the load applied, the voltages will deviate from 120 VAC to neutral, to 2-4 volts one phase and 240 one the other phase to neutral. the voltages remain very close to those values, practically no deviation of any kind with those measurements. I found a 94' schematic to the 8E unit that appears to be very close to the wiring scheme within the controller of this 1999 model. The bridge I previously mentioned monitors the b1-b2 values by providing a VDC input into the voltage regulator. A local friend will allow me to use his megger tomorrow to verify winding status. If stator windings are within specs, will supply a 12 VDC to slip rings and measure the generators output. All LED's are lit while running, relay indicators appear to be operating correctly. The generator was submerged 2 YEARS ago , not recently, in 'fresh' river water [ the Red river in north La.]. The owner was present when the boat was lifted from the drink and the first task he performed was to disconnect the battery supplying power to the unit. Will notify all of you kind gentlemen the test results that I measure, each unique problem represents a learning opportunity and this board allows all of us to share our knowledge. I'm inclined to align my diagnosis with Dan, the stator windings may be toast, though I hope not. The owner has no problem replacing the generator from a financial perspective, he's already replaced[via a local contractor] the main engine on the cruiser with a brand new one [460 turbo-charged Ford v-10] with no sweat. Many thanks for everyone's input and technical perspective. Richland
 

len k

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Last Subscription Date
12/12/2018
I failed to mention that no device becomes powered or can be turned on and operate when a single circuit breaker is turned on. When I leave a breaker on to supply some lights or other small loads, even with a voltage value of 40 volts on one phase and 240 volts on the other phase, no alarms are triggered of any kind. regardless of the load applied,

the voltages will deviate from 120 VAC to neutral, to 2-4 volts one phase and 240 one the other phase to neutral. the voltages remain very close to those values, practically no deviation of any kind with those measurements.
Sounds like connection between windings and output neutral are open or high resistance. The loads are forming a voltage divider of the 240. Happens in a house too when you loose the neutral connection to utility.
 

Richland

Registered
Once again Len, you are correct, the neutral and ground were very loose on the main terminals. Believe the problem has been found, the rotor brush assembly was a solid hunk of rust. Removed and carefully cleaned the entire assembly. Rotor rings were severely rusted, one brush was making no contact whatsoever and the wiring from the voltage regulator was also severely rusted, replaced screws, sanded slip rings, brushes in good condition including the copper 'pig tails'. Field winding [rotor] measured a respectable 6.3 ohms between rings, most stator windings measured within specs, though have not measured all windings as of yet. Many termination points require cleaning in the controller so that the new boards won't 'starve' for DCA, including fuse holders, starting relay terminals,ect. The owner is encouraged and has given me total latitude to restore the unit into a 'like new' condition. If all tests go well, might be able to start the genny tomorrow. There are many connections and component functions that must be checked and verified before I start the unit. Very tight, limited space means diagnostics take time, don't want to drop some part, screw,ect down into the bilge. Will post results once unit is running for at least an hour under a 75% load. After unit completes all load tests, owner wants me to join him and 2 others for a trip down the Red River all the way to the Gulf of Mexico, a distance of 330 miles; then we'll spend several days deep sea fishing in the Gulf, all expenses paid. Nice to motivation to 'do it right'. Thanks for all inputs and insight towards the goal of long term,correct operation.
 

LWB250

Registered
Be aware that the slip rings on the rotor are service parts - you do not need to replace the whole rotor.

They can be desoldered from the main exciter windings and pulled off using a gear puller, after the bearing has been pulled (if it's not inboard of the slip rings - I'm not familiar with the later alternator designs.)

I would replace the bearing and tolerance ring as well.

Dan
 

len k

Subscriber
Last Subscription Date
12/12/2018
After unit completes all load tests, owner wants me to join him and 2 others for a trip down the Red River all the way to the Gulf of Mexico, a distance of 330 miles; then we'll spend several days deep sea fishing in the Gulf, all expenses paid. Nice to motivation to 'do it right'.
Nice motivation. I hear on Navy subs the engineers who design it have to go on it's first underwater test dive. :D :eek: :yikes: :rant:

Also look arround for other corrosion problems, like I said it's likely spent at least a month in ~ 100% humidity air as the boat dried out in 80% humid outside air at the dock.
 

dkamp

eMail NOT Working
I've raised a few sunken boats, and things like this are an interesting challenge. The challenge is always TIME... from the time it comes out of the water, 'till it all gets dried out and running enough to stop ravaging corrosion...

I like to look at larger raisings like a 'team' effort... have at least one man for each engine, and one man for every 'critical item of recovery'... like HVAC, refrigeration, electrical distribution, mechanicals, even interior and upholstery... so that the moment she comes out, each system has 'it's own guy' to focus on getting THAT segment immediate attention.

For engines and generators, I prefer to get 'em up, in the clear, oil cleaned, cylinders cleared, started and running as soon as possible. Last one I did, I simply disconnected all field connections and the output breaker, so that when it started, it could produce no power, but was spinning. I got it started up, and ran it for 30 minutes, just letting it spin. Amazing how much water came out of the rotor during that time... centrifugal force did a wonderful job of clearing out what had gone in, and I imagine capillary action was hard at work with the closer windings... if it was cold, I'm sure that water would've frozen in and made a real mess out of the windings. Once the outflow of mosture eased off a good bit, I shut it down, hosed down all the brushholders with light lube, exercised them, started it up again for a few, shut it down, reconnected the field and load connections, and plugged in a load... I used some electric heaters to put about a quarter load on it, and let it churn, with the expectation that it'd warm up the windings etc, enough to dessicate the machine, which it did.

I think the worst part about going swimming, isn't so much the water, but everything ELSE that comes with it... mud, oil, and of course, the fact that it may be connected to batteries at the time- that can be really hard on circuitry. An auto-start circuit gone bonkers, could possibly attempt to crank an engine while it's submerged, and that's NOT good... the circumstances of a sinking don't usually permit one to take a walk through to shut everything down and prepare for a swim... bringing 'em back up is an adventure.

I dove down 9' once to bring up a runabout that'd sunk at the dock, and when I got down there, I heard a hissing noise... it was the bilge pump... switch was on, and it was faithfully at work, pumping water out of the bilge... That one was a rather crude recovery... I hooked a truck innertube around the lower unit, another under the deck, and used an air compressor to fill both... it brought her up to the gunwales, and a 5" trash pump got her floating high enough to trailer within three minutes... I got it ashore, rinsed it with garden hose, yanked the plugs, magneto and starter (outboard), rolled it over (blew the fish out of the cylinders), blew out the mag and starter with compressed air, then sprayed the ends well with some fogging oil, spun 'em a few times, put 'em back on, drained the carb bowls, hooked hose to the drive gills, and hit the key... started right up... never even took the battery out of the boat... and that danged battery continued working great for six years (it was already two years old!!!).
 

Richland

Registered
Many thanks to all resident experts who volunteered their valuable time and expertise to offer help and potential solutions to the problems I encountered. Final results revealed the rotor was fine, well within specs, voltage and current from the new regulator board worked quite well. After many hours of cleaning, verifying correct termination points with wiring,and even though the stator windings, batt. charge windings all measured less than 2 ohms between windings and infinity to ground on any stator lead, the problem ultimately was resolved by replacing the stator windings with a new 'set'. The problem with the stator would only become evident by using an old fashion, hand crank Starret megger that would produce 500 VDC to break down the 'resistivity' between the windings, though megger tests on the windings were clear [infinity] to ground. Unit is now operating like a new one, owner pleased, and a trip to the Gulf is planned first week in January. My error was that the Red river does not confluence with the Gulf of Mexico, it confluences with the Mississippi about 100 miles above the Gulf. The owner candidly announced it would be most beneficial for me to enjoy this trip with his fishing friends, he likes having 'technical' insurance on a long trip after major repairs, he insists I bring all of my test instruments, schematics and 'thinking cap'. He was also considerate to ask me what my favorite brand of brew pleases my palate. Thanks to all who helped me with this unique situation, I appreciate all input of wisdom and experience from the dedicated Stak crew. :)
 

len k

Subscriber
Last Subscription Date
12/12/2018
Old stator is likely still wet. Can try baking it at ~ 140 for ~5-7 days. In old days that's what they did in mills after floods, wash off with fresh water then bake. . Good to allow air exchanges so you don't end up with it in a 100% humidity ovan.
 
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