D1005 ( in Beta Marine 28 ) is not idling properly for a while after start - then runs good

Ursa Minor Beta

New member

Equipment
Beta Marine 25 ( Kubota D1005 )
Aug 31, 2025
5
0
1
The deep ocean
Hello! It's nice to be here.

After exhausting all my personal resources and reaching a dead end with my friends' advice, I'd like to see if anyone here in the specialist forum can help me out.

My boat's engine is a Beta Marine 28. It's based on a Kubota D1005 three-cylinder engine. It is not used often, as the boat sails most of the time.
In the last 5 years, it has been used for maybe 100 hours. However, rot is always a problem at sea due to the salt air.
In general the engine was started once a week to run all the systems and regular oil and filter changes and other maintenance work were carried out.

For some time now, the engine has been starting less easily (previously there were never any problems, and even preheating was not necessary at temperatures above 15°C).
Above all, it initially runs at very low revs when idling and does not respond to the throttle until it gets up to speed.

The first assumptions were, of course, air in the system, clogged filter, valve clearance, injection nozzles, compression.

I have now done the following:
I checked the entire diesel system and, as a precaution, replaced the hoses that had become hard.
I also annealed the copper seals on the overflow pipe to make them soft again for proper sealing.
I replaced all filters.

Injection nozzles checked (initially only roughly for leaks and spray function—no precise assessment made yet—I am currently far away from workshops that can do this and do not have the necessary tools on site) no obvious problems found.
Injection nozzles soaked overnight in brake cleaner to remove any contamination.
Glow plugs checked – working well.
Tested diesel supply manually from canister via engine with hand pump and filter directly into injection pump to rule out faults in the system.
Valves adjusted.
Engine shut-off device checked. (Magnetic switch removed and only the mechanical lever used).

Still to do:
Check compression – I don't have the right equipment for this at the moment.
Replace the injection nozzles as a precaution. However, I can't get hold of any spare parts at the moment.

After doing all this, the problem is basically still the same. Only the start-up has improved slightly. I think there was still a small amount of air getting into the system somewhere through the old hoses or seals.

Now it's always the same thing:
First, the engine runs at low speed when idling and doesn't respond to the throttle (adjustment screw or throttle lever).
After a while, the speed increases and it responds to the throttle again.
I've attached a video-link where you can hear the problem.
I can't tell if the engine is only running properly at low RPM or on only two cylinders. Maybe someone with more experience can hear it?
The problem also occurs when the engine is warm.
When restarting, it initially runs at low RPM. Only then does it speed up a little faster until everything is OK.
As long as it's not running smoothly, it emits a slight gray/black smoke, which means there is too much diesel in the system. (In one cylinder?)

As I said, I still have to do a compression test, and only replacing the injectors would rule out a problem with them.
But somehow that feels strange to me...
While looking through the parts list, I noticed this “idle apparatus.” (See Appendix ) It's somehow connected to the engine speed regulator, but unfortunately I can't find an exact drawing for it. Maybe there's something wrong there?

If anyone has had time to read through this novel, I'd like to say: Thank you!
And if anyone has any ideas, I'd say: Bring them on!

Sooty regards
 

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North Idaho Wolfman

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It's not firing all the cylinders at startup.
Bad injector or bad injection pump.

The next big port you land in get a big bottle of cetane booster and diesel injector cleaner.
It's not very likely to fix it but it might help mitigate the issue till you can dry dock and fix it properly.
Keep an eye on the motor oil level as if it rises even the slightest it might be putting diesel fuel in the oil.
 
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North Idaho Wolfman

Moderator
Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
33,756
8,966
113
Sandpoint, ID
The Booster part is 100% real and good, the cleaner part... well lets just say it's rolling dice at best.
But in your situation, it's the best bet for now.
Let us know when you hit a good stopping / maintenance point and can do some other tests to narrow down the issue.
 

Ursa Minor Beta

New member

Equipment
Beta Marine 25 ( Kubota D1005 )
Aug 31, 2025
5
0
1
The deep ocean
Ah. Ok.
Today I tried to use "diesel starter spray" and to my surprise that did make starting much easier.
SoI guess that would also point on the direction of faulty injectors? Or maybe the injection pump not producing correct pressure? However I guess the latter would also have an effect on non idle running?
 

Russell King

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L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
Jun 17, 2012
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Austin, Texas
Don’t use any type of starting fluid on these engines, you can easily make the engine become an anchor!
 
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Ursa Minor Beta

New member

Equipment
Beta Marine 25 ( Kubota D1005 )
Aug 31, 2025
5
0
1
The deep ocean
I see. Why is that? I guess the uncontrolled explosion is hard on the piston rings?
( I remember an old sailor who would start his engine with a dash of Bop insecticide...
 

Russell King

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Lifetime Member

Equipment
L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
Jun 17, 2012
6,637
2,203
113
Austin, Texas
As I understand it, the use of starting fluid in the intake air stream is flooding all cylinders with explosive mixtures that will explode in the wrong piston position and bend rods or damage rings as they try to continue the correct direction of rotation due to the actual firing cylinder from the injection pump and engine timing. These are not “real heavy duty“ engines so are more easily damaged than the larger diesel engines in many ships.

If you have time and the desire you could look at the spray pattern of the injectors and probably find the bad injector. You could also just order one injector and washer and replace the existing injectors one at a time to see if that improves the performance of the engine. Don’t buy aftermarket injectors just get OEM ones. The aftermarket ones are supposedly not reliable products.