30HP 3 cylinder rough idle when hot? Marine application.

[PenderBen]

Hello everyone.
This may be a bit off topic, but there is so much Kubota knowledge around here it seemed like a good place to ask.
Aside from my Kubota tractor we have a Kubota powered boat, an Albin 25 with a Beta Marine marinized Kubota 30HP 3 cylinder engine- unfortunately I can't find the engine model offhand, and the boat's out on a mooring at the moment.
The engine is nearly new, installed last year, and has about 7 hours on it.
It runs great, but a few times now has had some sort of problem at idle, which is about 800rpm.
The problem we're having is, after using the engine for probably around an hour at speed (between about 1800-2300 rpm) when we place it back in neutral and idle speed the engine runs very rough, so rough I think that it will damage the rubber engine mounts over time.
It runs smoothly at idle when cold, and it runs smoothly at speed when it's hot (anything over about 1100rpm).
We've tried rebleeding the fuel system, but can't really think of anything else to try.
Everything was redone when it was installed (cleaned fuel tank, all new fuel lines, water separator, filters, the fuel is fresh), it's fresh water cooled and hasn't gotten over probably 180f.

Any ideas what could cause this problem? Is it a problem (I know my B6200 idles pretty roughly too)?

Thanks for any thoughts on this.

 

[Tooljunkie]

The 3 cylinder diesels in the grasshopper mowers (22hp)do a similar thing after a few hours of hard work. But the idle would smarten up after a minute.

 

[North Idaho Wolfman]

The next time you are at the boat look on the flat spot next to the injection pump for a stamped in serial and model #.

Also you can get the CC off the side of the block (cast in) behind the injection pump near the rear.

 

[cviola2005]

Some of the 05 series engines have the model number cast in the side of the block below the exhaust manifold, in front of the starter. Also, some of the 05 series engines have the serial number stamped on a flat spot directly under the exhaust manifold toward the back of the block, above the starter. Other than that NIW is absolutely right.

30 hp 3 cyinder, fairly new, sounds like a D1305, though it could be a larger D1403, D1503, D1703, or D1803. If all depends at what rpm the 30 hp is rated.

 

[PenderBen]

Thanks all, I'll get those numbers next time I head out to the boat.
According to the specs I have come across it is an 1123CC engine.

 

[100 td]

.....it is an 1123CC engine.

Which probably makes it a D1105, EPA Tier 3, 29hp@3600
Check all fuel line hose connections, particularly the inlet side of the lift pump in case it's sucking a tiny bit of air at low revs when the hoses have heated up. At higher rpm of the lift pump, it may negate a small bit of air that affects it at idle. YMMV

 

[cviola2005]

100_rd is correct. 1123cc makes it a D1105. I overshot just a little bit on my guess.

When it as running rough, is it surging likes it cant keep the rpm steady?

With it having a water cooled exhaust, its probably running under the water surface so it can't be seen or heard, correct?

 

[PenderBen]

Hello, sorry for the slow response.
I finally got a chance to get at the engine.
It is in fact a D1305, and has 'K3A' cast just below that.
Not sure about the 1123CC designation, I just pulled that from the Beta Marine description.
Anyway, it's still doing the same thing, running rough at idle when hot. I checked all the fuel connections and they seemed good, but I didn't try 'messing' with them while it as running rough, so that might be something to try.
It idles at about 800rpm; it's normal/smooth when cool, and when hot and rough if you increase the speed to about 1000 it smoothes right out. It doesn't surge, steady engine speed, just really rough, bouncing around on its mounts.
It's in an Albin 25, so can be gotten at while running. My thought on next step of diagnostic is to get heated up, running rough, and try 'messing' with all the fuel connections to see if it makes any difference.
I don't think we ever bled the injectors, but did for sure up to the injection pump, could air in the injector lines act like this? I would think if there was air there it would run rough hot or cold, but it may be a simple thing to check.

Thanks again for any advice.
Ben

 

[al m]

Sounds like a lean " pop" to me,only two things with a diesel,air and fuel,either too much air or too little fuel to create the lean pop. I'm guessing,like others,something is loose,sucking air.Check it out while hot and the problem is there,don't be afraid of your wrenches and trust your senses,

 

[North Idaho Wolfman]

It does sound like you have bad injectors.
Could be valves are set tight.
Or possibility when they rebuilt it they set the injection pump timing wrong.


Feed it fuel strait to the injection pump and see if that changes.
If it doesn't change, check the valve lash, too tight of valves will do these things.
Then I would pull the injectors and have them tested.
If neither makes any changes you need to check the injection timing.

 

[PenderBen]

I'll see what I can do in regards to those suggestions.
It is a brand new engine with about 8 hours on it now, how likely is it to have valves misadjusted or bad injectors from the factory?

 

[100 td]

Is your fresh water coolant system staying EXACTLY the same level each time you check it when cold?

 

[Dave_eng]

Here is some info I found on line. 30 HP @ 3,600 rpm

Should this not be a warranty matter on a new engine?

Dave M7040

 

[lugbolt]

I'll see what I can do in regards to those suggestions.
It is a brand new engine with about 8 hours on it now, how likely is it to have valves misadjusted or bad injectors from the factory?

Not likely-unless the fuel quality is at question. And if in warranty, they'll inspect the fuel closely-possibly sending a sample off for a chemical analysis. It wouldn't be the first time I've heard of it happening. Reason being, they need to make sure they have a defect, and if not, they need to know what can be done to prevent it from happening again...

 

[PenderBen]

Doesn't seem likely to get warranty repair out of them, they just don't see to work like that, at least it hasn't been offered upon inquiry about the problem.
The tech at the shop we bought it from did offer to help diagnose it, if we can get it there, which naturally isn't that easy, even so that may happen.

 

[Dave_eng]

Doesn't seem likely to get warranty repair out of them, they just don't see to work like that, at least it hasn't been offered upon inquiry about the problem.
The tech at the shop we bought it from did offer to help diagnose it, if we can get it there, which naturally isn't that easy, even so that may happen.

Have you read this warranty info that covers your equipment.

http://www.betamarinecanada.com/pdf/BetaMarine_5Yr_Warranty.pdf

Travel for the tech to inspect is covered up to a certain distance.
Travel to do warranty work is limited to 2_ hours and 200 miles round trip. The removal and reinstallation of an engine is limited to 4 hours

I would not put a wrench on it until you force their tech to come.

Dave M7040