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Limp Mode Reset
This topic has 1 reply, has 2 voices, and was last updated by
4 years ago July 18, 2019 at 2:13 am Tuesday I ran out 90 miles to fish offshore and when we slowed back to idle to set up for fishing, my port engine alarmed with a fault showing “accelerator pedal or throttle low voltage” (SMX displays) and would not go above idle of 650 rpms. I have dual station Twin Disc EC300 controls. The problem affected both stations and it did not matter if the engines were operating in synchronized mode or with independent throttles. The ge…
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in: Cummins Marine Engines
1 ReplyJuly 19, 2019 at 10:25 am The only input I can provide is that if the engine sees a throttle voltage signal outside of the expected range, it will DE-RATE…. meaning the at the engine computer (ECM) thinks something is messed up with the throttle input signal and will de-rate the engines performance until the issue is fixed… my assumption is that this is 100% a safety issue….Last Post by:
posted: 4 years ago
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QSB Propping
This topic has 6 replies, has 4 voices, and was last updated by
4 years ago
July 11, 2019 at 7:12 am We have been having a real challenge attempting to prop a custom sportfishing 37′ boat with QSB 6.7 550s. The boat is very light at only 17,000 wet with full fuel and water. The problem is that the prop load appears to rise very sharply above about 28 kts, which we now think may be due to excessive stern lift generated by the props increasing hull drag. In order to get 3300+ rpms at WOT, it is necessary to carry no more than about 32 inc…
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6 RepliesJuly 15, 2019 at 6:34 am What makes this a complicated issue (at least to me) is that with my prior set of props that allowed the engines to turn up to the governor limit of approximately 3350 at WOT, the fuel rate at the speed the engines seemed comfortable cruising was actually quite a lot higher than in the current “overpropped” condition. For example, at 31 kts, the old props allowed the engines to turn up to 2700 rpms but I was burning about 18.7 gph p…Last Post by:
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Exhaust Gas Temperature QSB 6.7
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April 23, 2017 at 2:51 am I note from the specification sheet that the EGT at the turbo outlet for my QSB 6.7 550s is 970F. Ā When running at my normal “easy” cruise of 2600 rpms and around 50% load, I see an EGT reading of about 660F. Ā Is this telling me anything apart from it being very unlikely that the engine is overloaded? Ā The EGT does not seem to change a whole lot unless running at displacement speed. Ā It never gets up near the 970 reading even at WOT,…
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2 RepliesApril 24, 2017 at 11:25 pm Thanks Tony. Ā I did map the actual fuel curve against the published Cummins curve back when testing props. Ā I am within 5% from planing speed on up to WOT, being slightly above at the lower end and slightly below from 2600 approaching WOT of 3360, where I see about 95%.Ā By the way, the Cummins folks are still unable to diagnose the source of the knocking noise I asked about a few weeks ago. Ā They tried plugging the injectors one at a time and a…Last Post by:
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Knocking Noise
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March 31, 2017 at 2:44 pm One of my new QSB 6.7 550 engines makes a very distinct noise audible at idle up to about 1000 rpms that sounds sort of like the old fashioned “Diesel knock.” It is loud enough to be heard above the other engine noises but not much. It goes away immediately if the engine is put in gear. Ā The other engine does not make the sound, nor did the pair of QSB 6.7s I had on my old boat. The Cummins Atlantic people have had the diagnostic com…
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4 RepliesApril 3, 2017 at 8:58 am Thanks. Ā I asked the mechanic and apparently one of the things they tried was to unplug the fuel pressure sensor, which puts the pump to default mode of 12,000lbs. He also overrode the actuator raised the pressure to 24,000lbs. Ā Neither of those changed the noise. Ā Of course that is not the same as replacing those components but I wonder if what he did would have demonstrated a fault?Last Post by:
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Limp Mode Reset
