Detroit Diesel 6V92 DDEC 625hp engine lag issues

V

Viking 43 Capt

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Joined
May 5, 2014
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We are having an engine lag issue with our port engine. We have Detroit Diesel 6V92 DDEC 625hp engines. The problem exists only when we try to get the boat up on plane. The starboard engine does just fine coming up, but the port engine starts lagging at about 1,300 RPM and only makes it to about 1450 RPM until the starboard engine get the boat up on plane and then the port engine finally comes up and the boat runs fine thereafter at cruise speeds, but if you come back off of plane, the same thing will happen again trying to get the boat back up.

By way of background, the current and existing problem started only after we left the boat in the Bahamas this summer with some Bahamian fuel in it. The boat sat in the Bahamas for 45 days in the middle of the summer without being turned on or ran. When we went back to finally run the boat for a fishing trip, it idled fine but would not pass 1000 RPM when we put it under loan (went out to run it). I slowly was able to work some of this bad fuel out of it by reving it up in neutral and finally, the RPM?s started climbing. I was then able to get 1500, then 1800 and so on until the starboard engine came back. The port engine never really recovered and is doing what you see now. Since then, we had the fuel filters replaced (racor and secondary), the fuel tank polished (although this is new fuel), all fuel lines inspected and blown out, all injectors were pulled and sent to RPM Diesel for inspection (one was rebuilt because it did not atomize), and the turbo was pulled and inspected along with all other air sections of the engine. We also switched the fuel box/computer (ECM) and other sensors with the Starboard engine and nothing seemed to solve the problem. All of the stats say the engine is running fine, but clearly something is wrong, and it all seemed to start after that fuel issue in the Bahamas, but the entire fuel system was checked and cleaned out and nothing seems to be coming up wrong.

Can anyone offer any advice?
 
alldodge

alldodge

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Re: Detroit Diesel 6V92 DDEC 625hp engine lag issues

Viking 43 Capt said:
We are having an engine lag issue with our port engine. We have Detroit Diesel 6V92 DDEC 625hp engines. The problem exists only when we try to get the boat up on plane. The starboard engine does just fine coming up, but the port engine starts lagging at about 1,300 RPM and only makes it to about 1450 RPM until the starboard engine get the boat up on plane and then the port engine finally comes up and the boat runs fine thereafter at cruise speeds, but if you come back off of plane, the same thing will happen again trying to get the boat back up.

By way of background, the current and existing problem started only after we left the boat in the Bahamas this summer with some Bahamian fuel in it. The boat sat in the Bahamas for 45 days in the middle of the summer without being turned on or ran. When we went back to finally run the boat for a fishing trip, it idled fine but would not pass 1000 RPM when we put it under loan (went out to run it). I slowly was able to work some of this bad fuel out of it by reving it up in neutral and finally, the RPM’s started climbing. I was then able to get 1500, then 1800 and so on until the starboard engine came back. The port engine never really recovered and is doing what you see now. Since then, we had the fuel filters replaced (racor and secondary), the fuel tank polished (although this is new fuel), all fuel lines inspected and blown out, all injectors were pulled and sent to RPM Diesel for inspection (one was rebuilt because it did not atomize), and the turbo was pulled and inspected along with all other air sections of the engine. We also switched the fuel box/computer (ECM) and other sensors with the Starboard engine and nothing seemed to solve the problem. All of the stats say the engine is running fine, but clearly something is wrong, and it all seemed to start after that fuel issue in the Bahamas, but the entire fuel system was checked and cleaned out and nothing seems to be coming up wrong.

Can anyone offer any advice?
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:welcome: to iboats

The DD 2 cycle engines have been real good ones but the 625 HP ones have had more issues. Looks like you have done everything you could with the fuel issue so the leaves a restriction in fuel or air. Either leaking air past the connections, turbo or inner cooler not being able to produce sufficient pressure, or not enough fuel making it to the injectors.

You had the injectors looked at but what about the pump?

I would start with air leaks and such before going to the pump.

How is the lift pump pressure?
 
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