6CTA intermittent rpm issue

[egstasea]

I have a 2002 Tiara 40 Express. The boat is wide and heavy by design. I normally I have 1/2 fuel, 1/2 water, and 2 people, no dinghy or extra transom weight. It has (2) 6CTA-M3 CPL 8089.

I have recently developed an issue where the port engine does not spool up like the starboard, always on the first attempt of the day. The boost gauge for port stays on zero, while the starboard is building normally. The boat takes a hard left, so I don’t try for more than 5 or 6 seconds. During this time port is smoking black pretty good (even with underwater exhaust.) I bring the throttles up by hand not by synchronizer.

The strange thing is on the second attempt (and all subsequent) the port engine builds boost normally and the boat jumps on plane with the slightest trace of black smoke coming over the hump.

After the second attempt and both engines makes 2750 RPM (on confirmed tachometers) and 31 psi at WOT as it always has. I did note note EGT at WOT, but at cruise they are both at 900.

As a good student I have done some research and decided to look at the air side first. I cleaned the AirSep filters and checked the air side of the turbo. The filters were pretty clean, the turbo spins freely without any end or side play. The turbo on the air side was clean with a slight gray soot from AirSep.

I checked the bottom and running gear. They are clean, as I am in fresh water. Prop shafts spin freely.

Tested again with the same results.

Because I didn’t know what else to look at on the air side, next I changed the primary and secondary fuel filters, as I was going to do them in a few weeks any way. The old ones both looked good.

The boat came up on plane nicely on the next test. I thought I licked the problem, even though replacing clean filters didn’t really explain anything. I did note however this time the engines were both up to temperature before I first tried to plane.

Two days later the port engine did not spool up on the first hit, but did on all subsequent hits. The engines in this attempt where not up to temperature. Buy “not up to temperature” I mean trying to plane at 130-140 not 100 degrees.

Other possibly related information or red herrings:

– The after coolers where properly serviced 2 years ago. They where in good shape, again this is a fresh water boat.
– I first noticed this behavior after a 2 hour 10 knot cruise. I thought maybe the turbo was loaded up, so I took it for a hard run (after the second planing attempt) for 30 minutes.
– The long slow cruise was on my auxiliary tank with fuel from the beginning of the season. I wanted to use it before I lay it up.
– The port thermostat has been sticking for half the summer, it opens a late. They are 160 degree thermostats. I will throttle back if it gets above 190. Then it always opens, and I go on my way.
– I have always revved the engines after the first failed attempt to plane before the second good attempt.

To continue my troubleshooting I plan on doing the following:
– checking lift pump pressure on port during a plane attempt.
– see if I can replicate a good first plane attempt with warm engines (I never had to do this in the past)
– try two consecutive cold engine attempts without revving in between.

What really has me stumped is the problem goes away and the boat runs perfect. What else should I look at?

Topic

[egstasea]

Problem solved

The problem was the glendening synchronizer. I don’t use the synchronizor to bring it on to plane. The port is the slave motor and the throttle cable was not engaged at the glendenning.

The black smoke must have been the the starboard over loaded.
I have underwater exhaust, so it is difficult to see which engine is smoking.

[egstasea]

Aftercooler maintenance

I have had the boat for three boating seasons, I serviced the aftercoolers two years ago. They were serviced the Seaboard way. They came apart easily and had no corrosion. Because the boat runs so well, I was surprised how plugged up with black tar like oil they were. It cleaned up with a steam, air and wd 40. The bulk of the goo was in the mid section. The water side was clean as a whistle-again fresh water. The cores came out easy. It passed pressure tests on the first try on reassembly. I believe this is the first time they were ever serviced.
I have it from a good source, who cruised the previous owner extensively, that they cruise primarily at trawler speeds. I concluded that this type of operation plugged the aftercoolers, and when it was been operated at normal cruise level( like I do) the turbo and charge air plumbing heated up.
The boat also has 160 degree thermostats,which is not great for trawler speeds, but fine for cruises speeds.

I added the egt and boost gauges last year,so I can’t tell if it made boost easier after the aftercoolers were serviced.

The props were scanned when I bought it.

It can’t be over loaded when it makes 2700 heavy and 2750 at normal conditions can it?

I will photo tach it again before I lay it up for peace of mind.
I will also repaint the turbo for a new baseline.

[Philip]

Egstasea –

Sounds like you are on top of your maintenance on the AC? Out of curiosity, how did you clean the air side of all the black oily tar stuff? Got any pictures?

So you will for sure know more when you get the turbo off. But sounds like you are on the right track.

Keep us posted.

Phil

[egstasea]

Aftercooler maintenance

Twice today I have had replies disappear. Lets try this again.

I serviced the aftercoolers once in the three boating seasons I owned the boat – two years ago. I believe this is the first time they were serviced. I serviced they the “Seaboard way.” They came apart easy and had no corrosion. Upon reassembly they passed pressure tests on the first try. Because the boat always run so good I was surprised how plugged up the air side was. It was a black oily tar particularly in the mid section. The water side was clean as a whistle – again fresh water.
A trusted source, who cruised with the previous owners extensively, confirmed that boat spent a high percentage of its operation at trawler speeds. The consensus at the time was that the aftercoolers caused a restriction on the air side so when it was operated at cruise speeds, including my first season, the turbo and the charge air cooler heated up. The boat has 160 degree thermostats, which are not great for trawler operation, but fine for the way I run it.

I just added the boost and EGT gauges, so I don’t know if the engines made boost easier with clean aftercoolers.

The props where scanned when I bought the boat, the same time I phototached the engines.

I understand the concern about overloading, but if it is making 2750 light and 2700 loaded how can it be? I will phototach again before lay up.

I also plan on repainting the turbos when I have them off for service, so I will have a new baseline.

[egstasea]

Aftercooler maintenance

I have done the after cooler once in the three boating seasons I have owned it – two years ago. They were done the Seaboard way. They came apart easy and had no corrosion. I do not think they were ever done before I bought the boat. Cap bolts had paint on them and nothing appears to have ever been repainted. Since the boat has always run so good, I was surprised how gummed up (oily black tar) they were on the air side. Waterside was clean as a whistle – again fresh water. The consensus at the time was that since previous owner spent most of his time at trawler speed, the after coolers got plugged and restricted air flow. The boat has 160 degree thermostats which is not good for trawler type operation by the PO, but fine for the way I operate it. The trawler type operation was verified by a trustworthy person who cruised extensively with the owner. I concluded, when the boat was operated at cruise, including my first season, the turbos and charge air plumbing got hot.

I added the boost and EGT gauges after I serviced the after coolers so I can not tell you if the boat made boost easier after the service.

As far at the props go, they were scanned when I bought the boat. The boat has 750 hours, I have put 250 of those on it.

When I service the turbos this winter I will repaint everything and get a new baseline.

I know what you are driving at about overloaded. If I am making 2700 loaded and 2750 light, how can it be overloaded? I will photo tach again before lay up for piece of mind.

[Philip]

Egstasea –

The reason I was askin about RPM and Fuel burns is your turbo looks darker than normal. Both Bill and Rob noticed the same thing. It might be worth rechecking things as normal turbo color is a light tan especially if set up the way you state. Your turbo is darker than tan….

boats grown heavier as they age, tachometers wear possibly, props wear, etc…

What has been your aftercooler maintenance history, process, and findings?

[egstasea]

next step

Phil, The boat has always been able to make 2700 loaded to the gills. I don’t know fuel flow. I do have the original test data for this model which operates below the fuel curve. See attached pdf. My boat has 1″ less prop, makes 125 more rpm wot and is therefore even further below the fuel curve. My boat has CPL 8089, the boat was probably CPL 1929. My normal cruise rpm is 2200-2300, 22-23 knots and 900 EGT in a 1 foot chop, 1/2 fuel, full water, 2-3 people. Conditions are a little different now. See my response to Bill

Bill, I have come around to your thinking and my original thought. I was looking at some pictures I snapped during my last run and found the port engine was running at the same RPM as starboard (on glendenning sync), but about 1 psi less boost and 50 less EGT than starboard. It seems it might have some drag on it.

Trouble shooting is a funny thing, once you rule something out it is hard to come back to it.

I will take both the turbos off this winter and go through them as you suggest.

Yes the turbo is brown, Rich noticed the same thing. As I am very confident this boat is not over propped, I have not been afraid to run it. Not abuse it, but run it as it was intended.

[egstasea]

Brown gets lighter on the pipes, and even lighter on the incoming side of the after cooler, white on the outgoing side.

Confirmed Tachs with photo tach when I bought it 4 years ago.

[Rob Schepis]

Does that brown discoloration continue on the air pipe and into the aftercooler?
Does “confirmed tachometers” mean photo-tach?

[egstasea]

next step

Phil, The boat has always been able to make 2700 even load to the gills. I feel pretty confident that the boat is not over propped. I don’t have fuel flow numbers, but my speeds and rpms match Tiaras original tests very closely all across the board. See the attached test report. I realize that engine was probably an 6CTA-M2 not my-M3. That boat is just below the fuel curve. My props are 1″ less pitch. I usually run at 2200-2300 rpm and 16-18 psi boost, and get 21-23 knots in a 1 foot chop. Conditions are a bit off for the port engine now. See my response to Bill.

Bill, I have come around to your thinking. The last trip out the engines were at the same 2250 rpm, the port engine was making 17 psi with an exhaust temp of 850, while the Starboard was making 18 psi with an exhaust temp of 900. Seems like the port turbo has a little drag on it.

Troubleshooting is a funny thing, once you rule something out it is tough to come back around to it.

I will take both turbos off this winter and go through them.

Yes Bill the turbos are brown. Because I am very confident the engines are not overloaded, I have not been afraid to run to run them.

Thanks guys – Pete

[Bill Fuller]

Egstasea,

You would be surprised at how littler interference can cause a turbo to not spool up. Your turning it and then all was well indicates to me that you did indeed have a stuck turbo, even though you thought there was no resistance.

I have 2 first hand experiences with stuck turbos.
The first was a bout 10-12 years ago. After clearing the 5 MPH speed zone, I powered up and the port motor started belching black smoke and would turn up past about 1700-1800 RPM (Yanmars). After several tries, I went back in the bay and removed the air filters and spun the turbo by hand. I felt zero resistance, felt perfectly normal. I almost went back to the dock but decided to try one more time. Guess what. all was perfectly normal, as if the problem had never existed. The boat had not been used for several weeks. My exhaust is pretty good since Tony built it. About 5 years later had the same thing happen again after the boat had been inactive for like 3 months. But this time I had to use a wrench to free it up, then all was well. I did spray WD40 in both sides of the turbo to help clean things up. Used a soft brush to clean any “stuff” from around the blades. So, that was at least 5 years ago, never a problem since. Those turbos now have 5,500 hours on them and 17 + years.

Spray WD40 in the intake side, and clean things up. Then remove the riser and do the same to the exhaust side. Also post some pictures of the exhaust side of the turbo.

From the color of your turbos, those are some hard working motors!

Bill

[Philip]

egstasea…

Nice exhaust for sure….

question, what’s your fully loaded, full fuel, full water, full provision, loaded for bear max rpm?

And

What’s your fuel burn and rpm at cruise?

Phil

[egstasea]

Test results

Bill, thanks for the quick reply. A stuck turbo was my original thought too. Yesterday I did as you suggested and checked the turbo after the boat sat for 5 days. The turbo spun freely, and the boat operated perfect.

I am happy it operated well, but I am still a little stumped at this point. I have a hard time believing that there is any corrosion on the exhaust side as I have a vey well designed exhaust, and I operate in fresh water. I guess I won’t know for sure unless I take the turbo off.

Attached are photos of the air intake, and the exhaust for the port engine.

[Bill Fuller]

There is nothing strange about your issue.
The port turbo is sticking. The exhaust side.
Once freed up, it is good until the next time the boat sets for a day or so.
Open up the exhaust side of the turbo and see what you have (remove the mixing elbow).
Probably rust from water ingestion or something else.
I suspect if you try to turn the turbo after it has been inactive for a few days it will be stuck or hung up and hard to turn at least at first. Another thing you can do if you don’t want to look at the exhaust side first, is to remove the air cleaner (CCV) and free up the turbo before going out and see if the problem is gone.

Bill

[Author]

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