QSB 5.9 425 hp, high manifold temp ..help please

[Mark Plussa]

Hello,
We purchased a 2007 boat last month with twin QSB 5.9’s in it. Total hours 1050. The engine paperwork shows major work done on it including replacing the aftercoolers ( both core and housings), servicing the heat exchangers, new hoses, clamps, water pump impellers, raw water sea strainers sand blasted, and much more.
during the sea trial we had a high manifold temp and low manifold pressure alarm on the starboard engine above 2600 rpm. The diesel mechanic aboard swapped the IMT sensors, the problem appeared to followed the swapped sensor. But that was only part of it.

Since we took delivery I’ve replace the OEM Cummins IMT sensor two times. Getting the same results. Above 2600 rpm, alarm and Code 155 High IMT on the Smart Craft display. Throttling back immediately the alarm stops in about 1-2 minutes, and manifold temp decrease. The manifold temp split between engines is about 55 degrees.

I have a patient mechanic trying to solve our problem, but we are crashing an illusive problem. The “ new” aftercooler was removed and it looked ok. However, it was taken to a radiator shop to remove the stuck core. The core was not greased by the people doing the previous work obviously. They cleaned the water passages and claim it was 30% restricted water flow.
The mechanic is understandably cautious to blame that as the problem. When he reassembles it he plans to remove every hose and look for any obstructions etc.

Has anyone here had a similar issue?
Does anyone have any suggestions ? Is there any way to measure water flow volume from the pump?
Thank you in advance

Topic

[Clark Leighs]

Skiboat,

Try to send Mark a note.     I don;t know if this site allows that so if you can’t find a means ask  Seaboard.      If Mark filled in an email address it should be possible.   No guaranty he will reply.

[Joe]

Update?

Hi Mark, did you ever find a solution to this issue?  Mine is having the exact same issue.  Wondering if it might just be the sensor or if you needed a full service or something else.

Thanks

[Tony Athens]

Both aftercoolers…………………….. Get them on the bench and get the cores out..I don’t care what it takes… Obviously the past “mechanic” and your current”radiator shop” and maybe even your current mechanic has no clue as to what they are dealing with..

You are playing with fire.

[Author]

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