Have MAN D2848 403s in a 2000 Viking. Had an issue with a coolant temperature sensor alarm going off on port engine and changed the sensor, but alarm still going off. When changing the sensor I did straighten up and wire tie the wiring harness that was right there at front of the manifold but seemed fine. Now I also have multiple other alarms going off on the port engine and engine even went into limp mode but when shut panel off engine ran normal again. At one point the engine oil pressure alarm was also going off but that went back out. Slowed down, turned panel back off and on and boat ran fine, no alarms for 10 minutes or so, readings on all the gauges seemed normal. Slowed down and coolant pressure alarm came back. Once back at dock shut port engine down and restarted and reved up to about 1500 and the same alarms came back. See pic. One note, I did switch out the alarm panels for some newer ones a couple weeks ago as mine were pretty worn but first time I ran it, just still had the coolant temperature alarm still going off. Checked temps with IR gun and seemed to match starboard engine and fluids/levels all seemed fine. Any thoughts on where to start?
Sadly, it's going to take patience and in my case; lots of hooch. You have a bad connection somewhere. Somewhere is a supposed weather proof connect that has some green stuff in it. Pickup a few cans of contact cleaner and polish up every ground, connect, plug, terminal strip you can find. Including behind the dash that panel is mounted it. I keep WD40 in business; https://www.amazon.com/dp/B00AF0OFVU?ref=ppx_yo2ov_dt_b_fed_asin_title When in doubt of any connection. OHM it out from far ends. If not curable with this, you may have to call in a MAN tech in the lab coat (hate it when that happens). I have to state also, those Dan Foss senders suck. New does not mean squab to me.
Either the engine model isn't correct, or what you experienced wasn't limp mode. No such thing, on 100% mechanical engines like the V8 LE403. Regardless, my personal answer to your final question has to be... From a good MAN shop!
We have the 423 version, so dunno if anything is applicable to yours, but... We recently had a coolant level alarm on one engine (after some heat exchanger service just prior to winterizing last year), and a coolant expansion tank pressure sensor alarm on the other. Was told the engines are vary sensitive to coolant levels and the sensors are very sensitive to pressure levels. Sure enough, we were over a gallon of coolant low on the one engine, and replacing the expansion tank caps on the other seems to have solved that. I've also had to change an expansion tank sensor before too... -Chris
But that was my point, CR. I've owned a D2848 LE403 powered boat for 9 years by now, and while I can't still pretend to know 100% of those puppies, I'm quite familiar with them. But I'm unaware of any alarm-triggered "save engine", "limp mode", or whatever it can be called. BTW, if they would indeed have such feature, I'd be extremely curious to understand how it can even work, because there is absolutely nothing electrical or electronic in their Bosch pump and injectors: they are old school 100% mechanical, and AFAIK the only way to regulate how much fuel to throw at them is with the throttle-controlled governor, which is also 100% mechanical. The LE423 mentioned by Chris are very different animals even if based on the same V8 block, because they were the very first MAN engines converted to fully electronic common rail (among other modificaions, like the 4 valves heads) - and THOSE do have an alarm-triggered limp mode, of course. All that said, @LAM: I 'm not saying you're lying, and I take your word for it about what you experienced. But I can't for the life of me think of why and how that could happen!
I forgot to mention, we did experience RPM limiting when we had the coolant level alarm. I'd not describe it as limp mode, more like save engine mode... since we were still able to make about 1600 rpm (even though the manual suggest 1200). No similar symptom with the sensor alarm on the other engine. But again, we lave the LE 423s, not the 403s. -Chris
As I said, very different animals, the former being 100% electronic, vs. none at all in the latter. BTW, are you happy with your 423s, if I may ask? In Europe, they have a bit of a reputation for being a bit temperamental on the electronic side. Which - as I was told by a MAN dealer - was due both to being their very first engine converted to common rail, and to the assistance network not being yet up to speed on the new technology, at least in the early years...
