Low RPM & Black Smoke

[NoSpeed]

I have Cummins 6BTA5.9M3 330 HP@2800 RPM engines installed on our 2002 Bayliner 4788. The engines have logged approximately 1470 hours. I routinely operate the engines around 1500 RPM and cruise at about 8.5 knots. A couple of months ago, I was requested to pickup my speed to make a bridge opening and discovered the port engine would not accelerate to its rated RPM. In fact, the boat following me reported black smoke billowing out our exhaust during acceleration. Fire-walling the throttle was no help. Consequently, I had my mechanic investigate. At the dock, we took the port engine to 3140 RPM with no hesitation or black smoke. The air filters were cleaned at the end of last season. The primary/secondary fuel filters were also replaced at that time and vacuum gauges were installed. So, he said it could be the fuel injectors. Consequently, he replaced all 12 fuel injectors with new ones. On our next outing in mid-Sep, it was discovered this did not resolve the issue. The port engine could not sustain any more than 1790 RPM and the starboard engine would not accelerate past 2340 RPM. The discovery of the starboard engine having the same issue was not noticed earlier since I was using symmetric power. Now, my mechanic thinks it is likely to be caused by a torn diaphragm in the fuel injector pumps and suspects the use of Biobor JF as culpable. It has been difficult to get back on his schedule. Rumor has it he may have a serious health problem. Anyway, do any of you think this could be it? I am mechanically inclined to do routine maintenance myself. Would this be a job I could tackle or is it over my head? Where do I get the repair parts without buying completely new fuel injector pumps? Thanks.

Topic

[Tony Athens]

Metric Bolt Quality

Let me look tomorrow to confirm — That is our goal –12.9 shoulder/flange & zinc plated for all ..

COREY?? Remind me to look and take pics

Tony.

[NoSpeed]

Are the bolts sold at SB Marine made of class 12.9 alloy steel? Replacement Cummins bolts are class 9.8 medium carbon steel.

[Tony Athens]

You DO NOT want SS bolts , or AKA “Butter Bolts”..You want High strength Alloy steel 12.9 grade installed with a good anti-seize.

The rust is from SALT WATER internally seeping thru from the inside out.. You’ll “SEE” when the riser it off–Bet you high $$ IPA 6 pack..

Tony

[Rob Schepis]

Check out this thread regarding frozen bolts (see link below) and do consider the low profile extractors that I reference.

https://www.sbmar.com/community/topic/sheared-bolt-inside-c450-turbo/

[NoSpeed]

I have exposed the turbo bolts/washers and found them to all be seized. Penetrating oil, heat and tapping did not work. The bolts are no longer 10mm in size. Rust has degraded them to a size somewhere between 9 and 10 mm. So, I went down to a 3/8″ socket, which is 9.525mm, but they still would not budge. Rounding of the heads started. Consequently, I will need to cut off the heads with an angle grinder and am concerned what remains of the studs will not be easy to extract. I checked with Cummins. They sell the replacement 10mm Hex Flange Head Cap Screws for $2.12 each and the Plain Washers for $3.51 each. That is a cost of $45.04 for a set of 4. The cost of these turbo bolts/washers at SB Marine is on sale right now for $12, a set of 4! Could you tell me if these are SS bolts and brass washers, which would overcome the rust issue down the road? I think I should get my replacements from SB. Also, any other tips for extracting these bolts would be appreciated. If I fail, I guess it means the turbo has to be pulled and replaced, right? Thanks.

[Tony Athens]

90% chance you are on your way to much bigger issues.. ……………….Cut them off with a Makita cutoff wheel if heat, KROIL, & a good 6 pt wrench fail you……………..I’d be in a Hurry……………….I also assume you’ll be replacing all you have that are called “RISERS”..

Tony

[NoSpeed]

As far as I know, these Shower-type Risers are original to the boat. We are 2nd owners and bought it in mid-2013. It’s 1st lifetime was spent in the PNW, a salt water environment. Do you suspect this to be the root cause of my issue? As to corrosion, when my mechanic was installing the new fuel injectors, he commented about a need to replace the four bolts connecting the Riser to the Turbo Exhaust. Apparently, they need to be soaked in penetrating oil overnight before trying to remove them. Anyway, how should I proceed? Thanks.

[Tony Athens]

They are “Shower head Risers” and are the “worst of the worse” as to a guaranteed “Doomed to Failure” design..

Just look what’s inside and how they work… This is not rocket science as to what will happen when “something” corrodes thru. .. It’s all “By Design”, & it’s just a matter of time.

Tony

[Rob Schepis]

How old are those “shower head” risers?

[NoSpeed]

Last of 20 pics.

[NoSpeed]

More pics.

[NoSpeed]

Tony, here are more pics, but I do not see anything obvious. Thanks.

[NoSpeed]

OK. I will try to get some more pics next weekend. Thanks.

[Tony Athens]

Your pics are up so close, I cannot “see” what needs to be seen…………….Close-up are worthless as to seeing the overall..

Stand back / get back 2-4 ft — I want to SEE” the exhaust riser or “what ever it is that is attached to the turbo” and then where the 5 or 6″ hose goes……All angles, all perspectives from 2-4 ft away

Tony

[NoSpeed]

Final image.

[NoSpeed]

More pics.

[NoSpeed]

This weekend, I cleaned the starboard engine aftercooler. It was in identical condition to the port side. The following images are of my port engine exhaust system and turbo. The intake side of the turbo spins freely and there is no wobble or blade damage. The only obvious thing I saw was a droplet of oil clinging to the base of the intake side of the turbo. You can make it out in the next to last photo (Image 1318). More pics (17 in total) coming in following post(s).

[Tony Athens]

Your issues (low RPM & Black smoke) are “elsewhere” .. But do what we ask, and together we will solve it..

Tony

[NoSpeed]

Tony, yes, those pics are before cleaning. It will be another week before I can post photos of the exhaust system and turbo. I’m on it. Thanks.

[Tony Athens]

From your post, I cannot tell if the pics of the cores are before or after you cleaned them.

If before you cleaned them, then that is not your issue as to RPM or black smoke.

Pay very close attention to correct reassembly and do not deviate on anything to what I preach that way…

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As to what you suspect, your issue IS NOT because of your turbo leaking oil or has a bad oil seal..

I want to “see” your exhaust system including the turbo.. All of it. Air cleaner off, all angles & perspectives.

Tony

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