I've tried Everything....Yanmar with Sooty exhasut

[arcticmonkey]

could be you may need a bit more 02 in your engine compartment... I installed a 3 inch bronze pipe to improve air flow... worked well for me... added bonus less diesel smell in cabin

[saillr]

I had the same problem for years with my 1996 - 4JH2E. Finally tried FPPF Cetane 8+ in the fuel and it was much, much better. What fixed it for all was replacing the injector tips. Have had no trouble now for at least 5 years. The additive is a little expensive but you can dilute until you are happy with the results. It definitely improves the burn. I got a good deal from a distributor for a case.

[ozarkshark]

Been a mechanic since 1974. you have gotten good advice. My advice would be to have the injectors pop tested, they should spray fuel at a certain fuel pressure, the springs get weak in the injectors and they spray too soon and under lower pressure means less fuel atomization, and an early spray before compression has built to ignite the fuel. Any good diesel shop should have the equipment to check them. Most injectors have shims to adjust the pop pressure. If you have checked the thermostat for proper temp and the injector pump timing, the pop test is next. Not sure on your engine, but if possible try advancing the injection timing a couple degrees may help as well.

[Jimmy_G]

I recently had an issue with black exhaust smoke at high revs and found it was simply that I had a fouled prop.
I jumped in, scrubbed it clean and all has been well. However, I now need to clean it regularly until I take her out of the water and re-antifoul.

[FreeNEasy]

Wow, this forum is the business, thanks for all the suggestions.

I forgot to mention that we re-conditioned the head by cleaning out all the waterways, new valve stem seals, reground the valve seats and tested


I also cleaned all the rest of the engine waterways with Rydlime (very good) and fitted a new thermostat, washed air filter foam, spotless clean prop etc.

I cleaned out the pre-combustion chambers and fitted new insulators and copper washers so I'm sure I have just one installed but thanks for the suggestion. I also refurbished the sail drive unit so no issues there.



There's several other really good suggestions that I'm now keen to try so will be doing the following next:


1. Check that the thermostat is working at correct temp (80 deg C ? )

2. Getting the injectors Pop tested

3. Checking the injection timing again but this should have been done when the pump was tested and reset but no harm in asking what the timing was set to (15 +/- 1 BTDC is correct?)

4. Double check air intake

5. Diesel cetane booster - why not !



I'll give this a go and report back with progress.
Thanks again to everyone who chipped in !!

[Wotname]

Originally Posted by FreeNEasy

Wow, this forum is the business, thanks for all the suggestions.

.........


1. Check that the thermostat is working at correct temp (80 deg C ? )

.........

If the engine is a 2GM20, the thermostat will be 55-60C (i.e. raw water cooled)
If the engine is a 2GM20F, the thermostat will be about 80C (i.e. coolant cooled)

[karlos]

I am extremely interested in the outcome of this post, I have a Gib'sea 282 with the same engine 2GM20 raw water cooled and I have exactly the same issue and it appears that I have done all the same work to try and irradicate the promblem, I have already added an extension to the exhaust outlet but on a long journey it is still very evident the problem hasn't gone away. The only thing I haven't tried is the Diesel Kleen, on my next to do list.
Karlos

[skipperpete]

Has anyone tried the injection limiter screw on the governor housing. Read the service manual first and make absolutely certain that you can get back to the current setting by recording the length of the screw above the housing. Screw in for less smoke and out for more smoke. No more than ¼ turn of the adjuster screw at a time. There was a prior thread re this smoke/timing issue on a rebuilt 2GM20 by “broken pete”

[Mike Banks]

Your timing may be out. Engine may be running a tad retarded--

[FreeNEasy]

After reading the thread on a similar subject by Broken Pete, I'm going to try advancing the diesel injection timing but thought I'd check how to go about doing this.


When I had the injection pump tested, the shim was with the pump so I thought the Diesel shop would have checked the timing. But I'm not sure how they would do that??



I'm thinking that checking the timing is possibly done by trial and error using shims?? if so should I insert a thinner shim (lower the pump) to advance the fuel injection timing?



Any guidance?

[Compass790]

Originally Posted by FreeNEasy

After reading the thread on a similar subject by Broken Pete, I'm going to try advancing the diesel injection timing but thought I'd check how to go about doing this.


When I had the injection pump tested, the shim was with the pump so I thought the Diesel shop would have checked the timing. But I'm not sure how they would do that??



I'm thinking that checking the timing is possibly done by trial and error using shims?? if so should I insert a thinner shim (lower the pump) to advance the fuel injection timing?
\\

Any guidance?

The injection timing procedure is in the manual, best to follow that. It will tell you how to setup the injection limiter or just do it skipperpete's way
Yes removing a shim or putting a thinner shim in will advance the timing. Check in the CF library for a workshop manual if you don't have one.
Hope that helps

[skipperpete]

It's not complicated to adjust the injection timing but some care is needed. The method is called "spill timing" and involves removing the delivery valve on #1 cyl injector pump, re fitting the delivery valve holder and rotating the engine by hand until the flywheel timing mark appears next to the reference mark on the flywheel housing. Operating the lift pump manually cause fuel to freely flow from the open delivery valve holder but ceases at precisely the point of injection... "spill cutoff". If the timing is ok then the flywheel mark will be perfectly aligned with the ref point. Raising the pump makes injection later and lowering the pump( removing shims) advances the point of injection. You should read the manual for the finer details.
Of critical importance is the governor link to the fuel rack pin.... if that little pin doesn't sit in the U shaped cutout on the governor link the engine will suffer an uncontrolled runaway stoppable only by swift action to block the air intake.... or operate the decomp levers and risk dropping a valve.

[FreeNEasy]

Compass 790, Aren't the pump injection timing and injection limiter two separate things. The manual talks about waiting to see if diesel appears in the measurement pipe or at the connector when the timing mark lines up. Given the small changes, is it okay to go one shim size lower and give that a try to see if things improve?


I'm not sure I need to touch the injection limiter because she revs out pretty well and there's no problem with smoke from the engine.

[FreeNEasy]

Sounds tricky skipperpete....
you wouldn't recommend just shimming down a smidgin then just to see?

[skipperpete]

Personally I wouldn’t do that... much prefer to go the whole nine yards and get the timing perfect
That would advance the timing and possibly make the engine noisier ( than a GM diesel knock normally is). Be prepared to put the shim back in though.
The risk of missing the rack pin/slot alignment is the only danger.
The pump will lift out by moving the stop control lever to allow clearance.
I’m not really convinced that timing is the issue, those 2GMs can be off a long way with no apparent effect, I get wary when they run quiet though.