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cfoxcvg · 16-02-2010, 06:27

Quote:

Originally Posted by never monday

what's the max RPM in and out of gear?

Out of gear it will easily run up to 3100 RPM but I have not tried to go any higher out of gear.
In gear durring this problem I got it to 3400 RPM and I think it would of gone higher but I was afraid to push her not knowing what was wrong.
Before this problem I have had it up to 3600 RPM during some short test over the last few years. 3400 RPM was no problem in the past and I had to hit this point on occasion to get threw a local bridge with strong currents.

DotDun · 16-02-2010, 06:46

Don't be afraid to push the throttle all the way. The governor won't let it over-rev. Operating the throttle is simply asking the governor for a particular RPM, the governor operates the fuel rack on the injection pump. I'm not sure about the 2GMs, but my 3GM30s redline at 3850, one hour rated at 3600, continuous at 3400.

never monday · 16-02-2010, 07:04

please apply full throttle in and out of gear.
Report back RPM and smoke conditions.

cantxsailor · 16-02-2010, 07:40

On my old boat an even coating of small(pencil erasure size)barnacles on my prop gave me a similar sooty condition if I went over about 2/3 throttle. I found the engine was getting more difficult to start and eventually after checking the compression and finding it very low discovered I had burnt the exhaust valve seat. The engine had been running pretty well up to that point but at 30years old it was nearing time for a rebuild.

After the hurricane put the boat in a swamp I brought her home and while she was in the yard for repair I rebuilt the motor. It now runs like it should, no smoke, no trouble starting, no stalling. Check the compression before going the long way round. My bet is a combination of lower compression and crusties on the prop.........m

sigmasailor · 16-02-2010, 08:35

Are you able to get the boat to or over hull speed? If it doesn't maybe you have some internal engine damage or more likely just fouling (because of your previously leaking injector) of the exhaust channels including the mentioned elbow.
The timing issue (if there) seems too small to have any effect.

Tspringer · 24-02-2010, 21:39

Get a compression test before you start throwing money darts at parts.
Forget the guesses....get on with the tests.

Terry

cfoxcvg · 25-02-2010, 05:25

Well the problem has been fixed. I changed the shims and that fixed 75% of the issue. The next day I went out and cleaned the bottom. There was a small build up, no more than I have had in the past and there were a few small barnacles on the prop. After cleaning everything we are back in business. Water is crystal clear all the way up to 3400rpm and barley visible smoke is consistent all the way threw the RPM range.

I do think I am slightly over propped, I can only get 3400rpm wide open but I am not concerned being that there are signs that the engine is being over worked and there never has in the past. I am at my haul speed at 2700rpm for a strong cruise.

I can definitely tell the injectors were stuck, I could not here them before but now the sound is distinct and very recognizable, in all the motor is smoother and quieter then ever.

Thank You everyone for your help and input.

motion30 · 25-02-2010, 06:34

So the issue was injector timing?

cfoxcvg · 25-02-2010, 07:05

A good part of the issue appears to be injector timing although fowled prop was definitely also a factor. 75% fixed with shims and 25% after cleaning haul.
I would almost never jump to the timing issue except that this was a new problem showing up right after I did the injector pump work and I know I messed the shims up. In the future if there is any question then I will just replace the $24 shim kit. It also opened my eyes first hand as to how close the tolerances are with that pump.

Jesgatt · 18-07-2021, 06:56

Hi, I have a similar problem. My boat is a Dehler 36db with a Yanmar 2GM20 raw water. The engine used to run smooth and rev up to 2700 easily on load, however lately it is arriving up to 2500rpm (at max throttle on load), and black water and smoke is coming out of the exhaust. Tests conducted till today:

1. Engine starts immediately.
2. Conducted a compression test (by my mechanic) and the result gave around 400psi per cylinder.
3. Taken injectors for a service and injector nozzles have been changed.
4. Inspected stainless steel exhaust elbow and found out to be ok.
5. Tested engine off load and managed to rev it up to 3400rpm.
6. Inspected water locks and found to be ok.
7. Hull and prop are clean (even happened after it was hauled in with new antifouling).

Can someone please guide me on how to proceed? Do you think it is a timing issue? I am asking since I never touched the pump or shims before the fault developed.

Thanks

Compass790 · 18-07-2021, 11:46

Quote:

Originally Posted by Jesgatt

Hi, I have a similar problem. My boat is a Dehler 36db with a Yanmar 2GM20 raw water. The engine used to run smooth and rev up to 2700 easily on load, however lately it is arriving up to 2500rpm (at max throttle on load), and black water and smoke is coming out of the exhaust. Tests conducted till today:

1. Engine starts immediately.
2. Conducted a compression test (by my mechanic) and the result gave around 400psi per cylinder.
3. Taken injectors for a service and injector nozzles have been changed.
4. Inspected stainless steel exhaust elbow and found out to be ok.
5. Tested engine off load and managed to rev it up to 3400rpm.
6. Inspected water locks and found to be ok.
7. Hull and prop are clean (even happened after it was hauled in with new antifouling).

Can someone please guide me on how to proceed? Do you think it is a timing issue? I am asking since I never touched the pump or shims before the fault developed.

Thanks

I think you are overpropped for a start. You should be propped to be able to get to max revs driving. 2700 is quite a bit short.
Compression sounds fine.
Shouldnt be timing issue since you changed nothing but you could check it.
Check the governor & fuel rack linkages for smooth operation.
Best not to run it at black smoke blowing levels as it's not good for anything, just throttle back a bit till it burns clean.

We are overpropped too (Worse than yours) & have to monitor exhaust smoke.
You havent fitted a bigger alternator or anything like that have you?

**skipperpete** · 18-07-2021, 18:25

+1 for Compass790’s suggestions. Try removing the alternator belt and run it up again, are you doing the testing in the dock against the mooring lines? or underway?

Training Wheels · 18-07-2021, 19:14

Quote:

Originally Posted by skipperpete

+1 for Compass790’s suggestions. Try removing the alternator belt and run it up again, are you doing the testing in the dock against the mooring lines? or underway?

The alternator belt also runs the coolant pump.