671 TI Detroit dead spot in acceleration

Hi everyone. I’m new here and although I am an avid reader of the forum I am just now signing up. I have a pair of 671 TI Detroit’s in my 1988 12 meter Trojan. But I am at a loss regarding an issue I’m having. Background…. Engines are roughly 700 hours into an overhaul. About 3 years ago I was bringing the boat down from Maryland to Myrtle Beach. On my way home the starboard blew a turbo and she was blowing oil through the intake. I was able to nurse her into port in Myrtle. I replaced the turbo and gave her a quick test run, everything was well and good. Then due to life the boat sat for 3 years. Last month I started prepping her for the season replacing all fluids and filters. I took her up to River to fuel her up with about 200 gallons of fresh fuel but I ever made it. The port wanted to run run run but the starboard fell flat at 1500 rpm. I remembered that I never cleaned out after the turbo incident and figured the air box was clogged so I took apart the air box and cleaned her up. (Sea foam is a good friend). With that taken care of I had steady 500-600 rpm idle, a clean rev to 2400 rpm, and a smooth deceleration back to idle. When I took her out again I had the same problem, she fell flat at 1500 on the starboard side. She doesn’t smoke or bog down she just simply stops at 1500 no matter how far I push the throttle. Old fuel isn’t the issue as both engines run off the same fuel tank. Water temp runs 180 degrees or less depending on the load and oil pressure is steady at 60psi. Do I have an injector problem or a governor issue? Any help anyone can offer is appreciated. Thanks in advance.
-Greg

Hi,
Inline or V6 engines?
Just a couple of guesses.
This does sound like it could be a sticking injector rack.

But I also wonder if, as a result of the turbo failure, there might be some debris in the intercooler that you may have missed? Was the compressor wheel damaged?

Good luck.

In line 6. 671 TI detroit. I thought about the injector sticking but if if an injector sticks on this the systems are catastrophic. So I’m not convinced of that. Cfm is good.

Why do I feel like I know this boat. Can you post a picture?

2X's on the injector rack.... Check boost, check linkage......

I can’t post a picture from my iPhone

I did accidentally pull the variable speed governor when I was working on her. I was looking and went to throttle her up and yanked in the governor instead of the throttle. It may have messed with the setting.

As Paul Harvey used to say: "And NOW you know the REST of the story"!

If an injector binds going to full fuel it doesn't necessarily mean that it wouldn't return to idle. Your catastrophic scenario (run away) would NOT then occur. It's rare but I have seen it happen exactly that way IE: injector binds going to full fuel and stalls the control tube but the engine readily returns to idle and no fuel. Happened to me on a busy Los Angeles freeway in an old transit bus.

But, with what you just disclosed, makes me wonder if you bent something like the rack control rod. You might also want to look for interference in that area like a retainer pin or cotter pin out of position and hitting/rubbing the housing.

It's been so very long ago for me and I never was an inline tune-up guru so I'm probably missing something. But those are the things that come to my feeble mind.

Good luck.

Is the name on this boat "Hold fast"?

The original name of the boat was Santee. She came from the Chesapeake Bay Area about 4 years ago. Chris do you have any ideas on my problem? I have a mechanic coming this afternoon and I would like to avoid that bill if I can.

Well I found the culprit. The Intercooler is completely shot and plugged up.

Understandable. Not uncommon after a turbo failure.
Glad you found it.

I found a new Intercooler for $3000. Thinking about removing all of the remaining disintegrated fins and running it that way for a bit. Thoughts? It should still cool the air going in just not as efficiently.

You're going to alter the combustion efficiency equation doing that and be down on power while adding stress to your other engine. I think that you would find that you will blow through fuel and, at today's prices, it probably wouldn't take many hours of running to make you seriously reconsider.

You can get a rebuilt intercooler for much less than new and that's something you may want to factor into the decision.

It will have a lot to do with how you choose to drive the boat.

Just my 2 pennies.

jgmo said:

You're going to alter the combustion efficiency equation doing that and be down on power while adding stress to your other engine. I think that you would find that you will blow through fuel and, at today's prices, it probably wouldn't take many hours of running to make you seriously reconsider.


You can get a rebuilt intercooler for much less than new and that's something you may want to factor into the decision.

It will have a lot to do with how you choose to drive the boat.

Just my 2 pennies.

Click to expand...

I am a 1000% open to a rebuild or even a hood condition used cooler. Can you point me in the direction? Or even somewhere that I can send this one for rebuild? To be clear this is the cooler after the turbo but before the blower.

Crazy as it might sound, I'm fully aware of what and where an intercooler is. That's why I suggested it as a possibility for your issue in post #2 at the beginning of this thread. 40 years diesel mechanic and 7 years teaching the craft.

But I have been retired for a long time and my support and supply contacts have probably all changed "careers" too. So my recommendations would likely result in a "this number is no longer in service" message.

You might look at dieselpros.com. while I've never done business with them they might have what you need or could possibly point you to who does.

Good luck.

Oh man do they ever. Diesel pros have it all and they are not shy about asking for compensation for what they have. I found a company in Lockport, NY long since thought yo be extinct. Niagra Cooler. They make these intercoolers. $1800 each. Exceptional value in an out of control environment.

ok quick update. With my air flow now not restricted I still face the same problem. Would horrible under growth such as vegetation and grime on the shaft and prop cause this issue of reduced rpm? If you asked me last week I would have said no because diesels are just giant torque monsters that can’t be stopped by anything. However I’ve learned that naturally aspirated the 671 would really only run up to about 1500 under load at that point the turbo charger would start to spool giving the motor more power. Thoughts

You can sometimes find used parts at ebay.com or surplusman.com
With some searching, there are companies that make aftermarket intercoolers for many makes. Cheaper than from Detroit. Also there are Chinese makers of replacement parts found on alibaba.com There are Chinese makers of DD injectors that seem to run ok and make the same hp on a dyno.