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Discussion Starter #1
We have a Gemini 105mc with a Westerbeke 30B on it that we just bought. It is a 2003 and the engine only has 325 hours or so (didn't get used much). It sat on the hard for a year or so before we bought her. The engine was acting weird on the survey:

1. Idle rough
2. Some greyish smoke and leaving a little fuel sheen on the water.
3. But it ran well at higher rpms - 2500-3000 (max is about 3500 I think) even though it had the smoke.
4. It stalled a couple times at low rpms - idle shifting from forward to reverse.

We had a mechanic look at it and they thought they had solved this issue by doing the following:

1. Replaced a cracked metal return line off of the injectors (didn't solve it).
2. Replaced secondary fuel filter (I don't know if the replaced the primary - assumed that the would but as you see below, I found water in the bowl after running for 4 hours so now sure if they did).
3. Put in three new injectors to see if she ran good (one was bad, one was "wet", and the other fine so they are going to send off to be refurbished).

They thought it should be fine and just needed to be run for 4-5 hours to burn off the old fuel in the cylinders that the clogged injectors were letting in (that should get rid of smoke and sheen)? I did that and it started behaving worse.

1. Now, it will not get past about 2200 rpm and when it gets there, you get thicker black smoke and the exhaust spits out black stuff in the water. This is with the new injectors.
2. Still smokes (more white) at lower rpms and still doesn't idle the best.
3. Stalled on my twice today at low rpms struggling at idle trying to shift from forward to reverse - awesome for my 2nd time ever docking a catamaran!
4. I checked the primary filter and it had some algae in it and about half of the bowl was water, so I think the fuel must be bad.
5. This has two tanks and I realized someone had set up the tanks to pull fuel from one and return to the other (so the return tank was totally full). I fixed this by doing it right and pushing and pulling from same tank but only after back at the dock (not sure if this had anything to do with it).

So, the fuel definitely needs to be addressed (either with polishing or just removing it and putting clean fuel in it I assume). Can bad fuel cause these symptoms to happen? Does this sound like a more major problem? The mechanics are having a hard time with this so I would like to throw some ideas their way. I am also freaked out because I just closed on this boat a couple days ago and am afraid that the engine has a major problem here!

Thanks! Sorry for the long post with all the detail.
 

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I think bad fuel is a major source of your problems and would address it sooner, rather than later. Not knowing how many microns your filters are, you may be letting some algae by and risking clogging up your injectors again. The black soot out the tail is carbon from the improper combustion. It can also be a result of fouled props but it's probably a result of bad fuel in this case. The fuel sheen is a result of unburned fuel due to the incomplete combustion. It sounds like you would be better off removing the bad fuel and starting over than trying to polish it. If you still have problems after replacing the fuel you can look at timing but I think you should be good with fresh fuel.

Good luck!

Tod
 

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Discussion Starter #3
Thanks, Gladrags1. I am going to try to run fresh fuel through today and see what happens. If that makes things better, I guess I will have the tanks pumped and refilled with some fresh diesel. Keeping my fingers crossed!
 

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Dump the fuel, pull the tanks (takes about 2 hours) and flush them out.
- and join the yahoo group for Gemini's at Yahoo! Groups

It's a very active group.
Gemini Hull # 987 was mine until last September. The WB30b is a fine motor when treated right.
 

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Discussion Starter #5
Cleaning up the fuel helped the low rpm and black smoke issue but now we are back to the lighter smoke and light fuel sheen on water. The mechanic said that would be normal for several hours because of the problem injectors which would have allowed some fuel to glaze in the cylinders. We need to run the engine for 4 or 5 to burn that off and that should get rid of the smoke. Does that happen that old excess fuel needs to be burned off like that?

I joined the Gemini group on Yahoo as well. Thanks!
 

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... Can bad fuel cause these symptoms to happen? ...
Definitely.
Do not run the engine again without at least draining the water out of the water separator, and changing the filters. Clean your tank. If you haven't already checked a recent post "How much water in the fuel filters is Ok?" you should do that it is very informative on why and how to keep the fuel tanks healthy.
 

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Idle on the 30B Three should be at a minimum of 1000 RPM and a max of 1200 RPM set it wherever it needs to be within that range to smooth it out. Too low an idle can damage things such as damper plates, mounts chafe wiring etc. etc...

You will probably want to confirm this with a digital photo tach as the engine tachs, which are driven off the alternator, can't be entirely trusted to be very accurate.

Change the filters, change or polish the fuel, clean the bottom & prop, confirm tach is correct, confirm throttle cable is moving full travel, adjust idle then go run her pretty hard gradually increasing RPM up to max RPM/WOT and then let us know how she runs...

How clean is the bottom & prop?
 

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Did your engine problem get resolved by replacing the diesel fuel? Currently experiencing similar issues with my Gemini 105M
 
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