Boost Down 1 lb at Cruise

[pwrobert]

No smoke, engines run good, but notice that the Starboard engine Boost Pressure in no longer matched to Port \.  I have the Seaboard Dual engine Boost gauge and normally the two needles are one over the other.  Now at 2400 the Stbd  (8) is about 1 lb less than the Port (9).  

I have Seaboard exhaust system and serviced the After coolers about 10 months ago.  Do Fresh Water Flushes on a regular basis.

My list of things to check are: Re-service the aftercooler, remove the exhaust flange from the turbo and inspect.

Which should I do first?  Trying to keep the disassembly to a minimum.  Or are there other things I should be checking as well?

5.9L 6BTA 370 with 220A Transmission, 4 blade nibral 22X20 prop that has been previously calibrated to SB specs.  Fuel burn is same as before as far as I can see.  Maybe could be off a tenth or two but I don’t have accurate numbers for the Stbd engine as I only recently got the Maretron Fuel analyzer fully calibrated for the Stbd engine.

Topic

[pwrobert]

Follow-up

Turns out I just could not let this go and had to take things apart to satisfy my mind.  Here is ehat I found – core came out easily and all looked pretty clean on first inspection of the upper portion of the core.  But turning it over was another story.  I could see deposits from the zincs all around a few of the cores water tubes.  Fitting a small rod in the openings I found  that not only those few that looked plugged but probably 40% or more were either fully or partially plugged.  

I have a heat exchanger /aftercooler rod for cleaning out theses passages and did each one until it was smooth and free.

As soon as the Seaboard o-ring kit gets here I ‘ll put it back together and report back the boost readings.

Engine never showed any rise in water temperature but the inefficient coolong of the hot turbo air in the aftercooler is my bet as to the 1-2 PSI drop in boost.

 

 

 

[pwrobert]

Thanks for the suggestions.  My filters are changed regularly and have SMX vac gauges on them as well.

Bottom is pretty clean – was hauled in June and cleaned and touched up.  Port Prop has new Propspeed on it as of June but the Stb one was last painted back in early April and looked good when out in June for other issues.

Due to very low summer tides the boat was run only a couple of time between June and Late September  as I can’t get out of my canal when we have those extra low tides.  Now with the Fall normal and King tides that is not normally an issue.  I’ll try and run the boat  a little more and maybe make a long run down South for an overnight and see how things measure up after that.

 

Spent the down time locked in the canal to strip and re-varnish the Galley, bunks and head.  Always something to do.

Thanks again.

 

[Rob Schepis]

Yea nothing to get too crazy over … Many hours on the fuel filters?  Maybe change them out and then you can cross them off the PM list anyway so win-win.  Prop geometry could have been slightly effected changing the load on that engine just a tad.  

[Dave Carlson]

I was told by a Cummins mechanic I was anal when I asked him about a 5lb difference between engines on 480CEs! I would not worry about 1lb. 

1 user thanked author for this post.

pwrobert

[Steve Lewis]

Quick thing to check….

PWR,

Boost and EGT have been on my mind lately.  I had 1 clamp break on my turbo air pipe.  An easy thing to do is make sure all of the clamps that hold rubber boots on to metal pipes are snug and not leaking air.  If your air plumbing is like what I have seen on the “Engine Start” videos of the 6BTA370 then that should be a rather quick easy thing to check/rule out.

 

1 user thanked author for this post.

pwrobert

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