• If you like antique engines, vintage tractors or old iron, please register and join us. When registering, please provide your CITY and STATE as your location!

Kohler 7.5R Marine Unit, Surging/Hunting Under Load Only

Vanman

Subscriber
Last Subscription Date
07/10/2019
It sounds like you're making good progress! Ultimately you can probably get even better regulation. In my opinion 63 is too fast. I like to set them up to run 60 cycles at 1/2 load. With a well adjusted carb and governor, you might be around 61-1/2 at no load and 58-1/2 at full load.

The voltage can also be adjusted. It will drop a little when the generator warms up, but does sound too high. There is a resistor under the brush cover. It has a moveable band on it that can be loosened and moved to add or remove resistance in the field circuit. Careful with it, the resistor is somewhat fragile. At the same time, make sure everything is clean so you get a good connection when you tighten the band. Moving the band towards the end of the resistor that the band's wire connects to will lower the voltage. Trial and error will be required, and you'll want your speed correct first.

Another adjustment that I don't think has been addressed is the governor arm to throttle linkage. I do not have first hand knowledge of how this specific one is to be adjusted, but ordinarily you want to adjust the length of the rod such that it just holds the throttle at wide open with the engine stopped. So the spring is pulling the governor as far is it will go, and the linkage is just holding the throttle at full, but not really trying to push it further.

There are flyweights inside the governor that move to pull the throttle towards idle as speed increases, while the spring is pulling in the opposite direction, towards wide open. Where the two balance is where the speed will settle. But there is only a certain amount of travel within the governor. This is why you normally start the adjustment with the governor at the end of it's stroke at rest.

Looking at your photo it appears that the governor arm is not moving as far to the right as it should, presumably being stopped by the throttle.

I think your spring looks correct. It may be stretched I suppose. When slack does it collapse all the way?

I think I'd use the lowest hole for the spring, such that it can pull the spring further when the speed adjustment screw is turned further in. As the governor is set more sensitive, the spring will need to pull harder, so it has to be able to be stretched longer.

Here's a photo of a governor from a 1963 L600 engine. Looks remarkably similar. Notice the angle of the governor arm is a bit more to the right. This one has only one hole for the spring. And it's speed adjustment screw is broken off...

Keith
 

Attachments

Last edited:

jack0

Registered
Age
60
I believe the throttle linkage is to long. Compared to mine it looks like there is a fair amount of exposed threads on the end that I can see. My linkage is 7" long. Ball stud to ball stud.
 

stevegnh

Registered
You really are being a huge help, thank you. I wish I could get down there asap and keep tweaking, but work calls. I will be down Thursday night hopefully, and if not, Friday for sure. Thank you.

I like to set them up to run 60 cycles at 1/2 load. With a well adjusted carb and governor, you might be around 61-1/2 at no load and 58-1/2 at full load.
Thanks, this sounds like a good plan. I will do that.

The voltage can also be adjusted. It will drop a little when the generator warms up, but does sound too high. There is a resistor under the brush cover. It has a moveable band on it that can be loosened and moved to add or remove resistance in the field circuit. Careful with it, the resistor is somewhat fragile. At the same time, make sure everything is clean so you get a good connection when you tighten the band. Moving the band towards the end of the resistor that the band's wire connects to will lower the voltage. Trial and error will be required, and you'll want your speed correct first.
Thank you. I'm not familiar with working in/around the brushes, so I'll have to look in the service manual for that. Does it require major disassembly to get at them? I hope not, due to genset access. It's not terrible, but I'm usually sore after working on the sides of it after a while. ha ha. For setting speed first, I should be doing this by focusing on the frequency, correct, since there's no RPM gauge. I have a handheld tach, but getting it on the flywheel is tough.

Another adjustment that I don't think has been addressed is the governor arm to throttle linkage. Looking at your photo it appears that the governor arm is not moving as far to the right as it should, presumably being stopped by the throttle.
I will check this to be sure.

I think your spring looks correct. It may be stretched I suppose. When slack does it collapse all the way?

I think I'd use the lowest hole for the spring, such that it can pull the spring further when the speed adjustment screw is turned further in. As the governor is set more sensitive, the spring will need to pull harder, so it has to be able to be stretched longer.
Yes, it collapses all the way when not extended. So you are saying by lowering it to the bottom hole, it allows the spring to stretch longer when needed? More travel room? When I had it there for a trial, there was slack I couldn't get rid of in the spring. It was sloppy. But that could be related to the linkage arm length being off.

---------- Post added at 09:41:31 PM ---------- Previous post was at 09:40:05 PM ----------

I believe the throttle linkage is to long. Compared to mine it looks like there is a fair amount of exposed threads on the end that I can see. My linkage is 7" long. Ball stud to ball stud.
Thank you Jack. Is yours a 7.5r23? What year? I wondered about the linkage length already, but couldn't find any spec to confirm it with, but I had a feeling it was too long. If so, I can TOTALLY see how it would help to shorten it, based on what VANMAN explains. I will definitely double check this with a caliper, ball center to ball center, for 7".
 

stevegnh

Registered
@VANMAN, I looked over the service manual and located the brush cover. There is no mention of the adjustment on the resistor to adjust voltage though. Is this on all of these units?
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Unfortunately I do not know if all had the adjustable resistor. But the cover is easy to remove to have a look see. Should be just a few screws holding it on.

Should look in there and see that all of the brushes move freely in their holders and are of adequate length, and that the commutator and collector rings all look good. Should be a nice, even dark color. Not bright and shiny, but no burned spots.

Keith

---------- Post added at 02:03:59 PM ---------- Previous post was at 02:02:03 PM ----------

Sounds like your spring is still good.

If you use the bottom hole, then turn the speed adjustment screw in, would that give enough pull on the spring?

Mine was missing parts, thus I had to improvise, so I do not have any hands on experience.
 

stevegnh

Registered
Unfortunately I do not know if all had the adjustable resistor. But the cover is easy to remove to have a look see. Should be just a few screws holding it on.

Should look in there and see that all of the brushes move freely in their holders and are of adequate length, and that the commutator and collector rings all look good. Should be a nice, even dark color. Not bright and shiny, but no burned spots.

Keith

---------- Post added at 02:03:59 PM ---------- Previous post was at 02:02:03 PM ----------

Sounds like your spring is still good.

If you use the bottom hole, then turn the speed adjustment screw in, would that give enough pull on the spring?

Mine was missing parts, thus I had to improvise, so I do not have any hands on experience.
Thanks for the reply. I'll look for the resistor. If it's not there, not sure how the volts come down and keep the frequency where it needs to be.

First thing I'll do is check the length of the linkage between the carb and governor, then move the spring, and see what I have.
 

Zephyr7

Registered
You’ll be looking for something like the attached pic. The band will have a screw in it that lets you loosen it for adjustments. Slide a little one way or the other and retighten the screw to lock in the adjustment. Don’t adjust it while the set is running.

Bill
 

Attachments

jack0

Registered
Age
60
Steve,
I have a 67 6.5r61-L654. Kohler side draft carb. Should be identical to yours. I would think if you shorten the throttle linkage it will put the gov. in a more happy range of adjustments.

Not sure if you have the adjustable field resistor. Its hard to tell with the Kohler model numbers. You might have the L654 engine with a rotating field generator. If that's the case you have a solid state regulator. If you have no starter on the engine you will have an adjustable field resistor and you could trim the voltage.

I remember a post a few years back. Someone with a marine 120v. 4-5 kw set with a field resistor and no compounding transformer. If this is the case with yours you will notice that the voltage might not be spot on. Slower to get back up.
Might not be a bad idea to open up your controller and see how it looks. A good time to blow out the dust.

I don't think you mentioned what year generator this is.
Kohler used the L654 with both the rotating and stationary field sets.

I'm sure you'll have it running right in no time.
 

stevegnh

Registered
Thanks for the picture of the Zephyr7, that helps so I know what I'm looking for.

Jack, thank you. My generator is likely made in 1987-1988, as it's in a 1989 model year boat, manufactured in 1988. Is that a typo in your post, where you said you have a 67? Did you mean 87? My engine is the L654 for sure.

Can I ask you a few questions?

Is your governor speed arm like mine, with 3 holes for the spring, or like the one in the service manual picture I posted (which doesn't match what I have), showing a boomerang shape and only 1 hole for the spring. I will definitely check my throttle linkage though. I feel I'm very close now to getting it dialed in.

You mention a solid state regulator. How would I know? I know my generator is a relay model, not solid state, but I don't believe that is what you are talking about in regards to the regulator.

When you talk about "opening up the controller," do you mean open up the control panel, where the relays and circuit board and wiring is? I had it open when I hooked up the electric fuel pump. It was very clean and mint in there, I was surprised how good it looked.

And what's the difference between a rotating and stationary field set, and how I would know what I have?

I'm obviously learning a lot as I go. I'm very handy and capable with tools, electronics and AC power, but getting this deep into a genset is new for me, so I'm just make sure I understand fully before I move on to the next stage. Kind of the "measure twice, cut once" model. :)

Thank you all so much!
 

jack0

Registered
Age
60
Steve,
No typo on the year. 67 or 68. L654.
The gov. speed arm is like the one in the manual.
Yours is an 88 so you have a rotating field set. The magnetic field is the rotor. The regulator is sensing your voltage and provides d.c. power through 2 slip rings to control the field strength depending on your loads. Power is taken off the outer stationary coils.

My unit is old school. Opposite of yours. Power is taken off the rotor or armature with a few cool features. The armature also provides d.c. for relays, field and battery charging with the appropriate resistors. These older ones also had 2 sets of field coils. 1 resistor in the bell end controlled field strength in 1 set and a.c. to the loads were run through a compounding transformer. The transformer secondary was rectified to dc for the auxiliary field. Voltage is quite stable. More current through transformer more power to the field. Also on these old sets the generator turns for engine starting.

I'm not very familiar with your set, but I'm sure there are a few relays for starting, ignition, battery charging etc. If you have a circuit board its most likely the regulator.
 

stevegnh

Registered
Thanks. I popped off the brush cover, and nothing to adjust. Here's what I have, see the pics. I'll work on adjusting the linkages and see where I land.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Oh yes, sorry, that is indeed a stationary armature / revolving field generator. I was not visualizing that. I am not familiar with their regulation either, unfortunately. But we should still be able to help get the governor and carb squared away in the meantime.

I don't recall, did you end up getting a schematic for this set?

Keith
 

stevegnh

Registered
I have wiring diagrams from the service manual, that's about all I have though, but should be good. I do believe I've made some significant progress though.

Using the guidance from Vanman, I double checked my linkage length. 7" on my unit is too short. It would not allow the carb to open fully. It was at 7.5" before I touched it. I double checked, making sure the carb and governor connection allowed full movement to the limits of the carb and governor. 7.5" was dead on, so that was right.

I then got into the adjustments for speed, sensitivity and finding the right hole for the spring. In the bottom two holes of the speed arm, the sensitivity adjustment had to be set to the least it could be to actual let the governor adjust for load, but it wasn't enough. The spring wasn't tight enough. The top hole seems to do it best, and you will see, the eyebolt is not on max sensitivity, so I have some room to work.

So all that being said, I adjusted the speed screw for 61 hz at warm idle. My voltage reading is still high to me though, at 143 volts. I'd rather see 61hz and around 130 volts.

Anyway, as I load it down though, the genset responds very well. With a pretty heavy load (1500 watt space heater, 500w floddlight, hot water heater, fridge, icemaker, and cockpit freezer), she was sitting right at 59-60hz and around 120volts. Very happy with that.

Here's some pics and videos. Videos are links to dropbox showing genset operation under this heavy load. You can see the fluctution in voltage, freq, and the governor performance.

The static pics of volt and freq are at idle, no load. And another pic is included to show the current eyebolt setting for sensitivity.

So very close I feel. So thank you all. Only two open questions:

1. Is the level of movement in the governor still considered "light" hunting/surging? Should I try to adjust sensitivity more? Make it less sensitive?

2. Given the type of genset this is (no ability to adjust resistor at brushes), is there any way to get that idle voltage down?

Frequency under strong load:
https://www.dropbox.com/s/ojcpx5pzw47403w/Video Jun 28, 12 54 03 PM.mov?dl=0

Voltage under strong load:
https://www.dropbox.com/s/qyowiwcp59k7miq/Video Jun 28, 12 54 14 PM.mov?dl=0

Governor movement under strong load:
https://www.dropbox.com/s/ju3uvmha8a5q3p7/Video Jun 28, 12 54 29 PM.mov?dl=0

Open to opinions, thoughts and advice. Thank you!
 

Attachments

stevegnh

Registered
Oh and one more...I haven't had the courage to try the ACs yet, as I'm most worried about doing damage to them if the genset is off. Same with the battery charger. Thoughts on adding those for a test? Heading away for 3 nights on Wednesday with boat. Would love to have faith in the genset to support the outing beyond lights and and the fridge.
 

Zephyr7

Registered
61Hz is good. 150v is TOO HIGH! 125v is really the highest to be within line voltage specs, but you can usually ge away with up to 130v without damaging things.

I would NOT try running anything important on that genset before you get that voltage under control. Stick with resistive loads like heaters and lightbulbs for testing until you’re SURE you have things running right.

Don’t you have a voltage adjustment on this set? If not a pot or rheostat, at least an adjustable resistor with a sliding band?

Bill
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Ah, well, getting there. But the throttle shouldn't really be moving at all under a constant, steady load. Still something going on with the engine, evidently, either carburetion or ignition.

Your carburetor is completely different than mine, so that explains the difference in the linkage.

As I said, I have really no experience with this modern of a set, especially the revolving field type of generator, and the schemes used for their regulation.

But, I'm wondering if this doesn't have some sort of "inherent regulation", rather than the "automatic regulation" (electronic AVR, "Automatic Voltage Regulator") more typically found on the newer stuff. The reason I say this is that an AVR (that's working right) will not allow such high voltage, and will generally keep voltage fairly constant, even as speed and load vary, within reasonable limits.

Can you get more photos of the set, especially the controller? Maybe some photos of what's in it?

Here's a video of mine from several years ago. This is taking the load of a 5000 watt lamp, all at once. Look and listen to how dead smooth and steady it runs, both with and without load. This is how yours should run. I had the carburetor dialed in nicely, but it still had the monkeyed governor linkage at the time, so the regulation is actually poor. Yet, at the same time, not too bad. When everything is right, they will actually regulate quite a bit better than this, both speed and voltage.

https://www.youtube.com/watch?v=7-pcwto-ofI

Keith
 

stevegnh

Registered
Ah, well, getting there. But the throttle shouldn't really be moving at all under a constant, steady load. Still something going on with the engine, evidently, either carburetion or ignition.
So should I try to adjust the sensitivity a bit more then you think? I basically quit while I was ahead. :)

Can you get more photos of the set, especially the controller? Maybe some photos of what's in it?
I will sure. When you say the controller, you mean the box with the fuses, genset wiring, test/off/remote switch, etc?

Here's a video of mine from several years ago. This is taking the load of a 5000 watt lamp, all at once. Look and listen to how dead smooth and steady it runs, both with and without load. This is how yours should run. I had the carburetor dialed in nicely, but it still had the monkeyed governor linkage at the time, so the regulation is actually poor. Yet, at the same time, not too bad. When everything is right, they will actually regulate quite a bit better than this, both speed and voltage.
Thanks, very nice actually. I'd be thrilled with that.

---------- Post added at 06:54:09 PM ---------- Previous post was at 06:52:11 PM ----------

This may use the infamous Kohler #233833 voltage regulator.
Infamous.Sounds like a known bad part? And if I had to guess, maybe hard to get...Any more information you can share, I would appreciate it.

I'm supposed to be going with the boat for 4 days and 3 nights, and sounds like I'm not going to have a solid generator to run things like the fridge, AC, etc. :(
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Based on the speed regulation you're demonstrating and the appearance of your governor settings, I do not think the governor is too sensitive.

I think the surging / hunting is most likely carburetion. Let's not forget the possibility of a vacuum leak either. Throttle shaft, carb gasket, intake manifold gaskets, hopefully not a cracked manifold.

But, above all, before powering stuff we need to figure out why the voltage is so high / regulation so poor. That shouldn't be, especially now that you've got the speed regulation better.

Keith
 
Top