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About Colic

  1. My apologies for not posting the resolution. Apologies also for the delayed response jfed, Ive been overseas. The problem is that the mercruiser ECU (in my engine anyway) does NOT report the Guardian cause for this particular fault. I confirmed this with the manufacturer who agreed I should have seen a fault code but indeed did not. What the ECU should have said is "low seawater pressure at revs". But instead it simply shut down the engine with no clue as to why. And there, in essence, you have the explanation. What would have made the diagnosis easier would have been a running test on the water with the scan tool, where I would see reasonable, but below par seawater pressure as the revs increased. But on the hose, the pressure is so low as to not make a difference in the readings. After stripping and rebuilding the pump, to no avail, the next likely culprit was the intake hose where it comes through the hull, as this is a known problem. I purchased a stainless replacement from Aftermarket Marine which I managed to fit after removing the leg (but not the housing). Again on the hose, no difference, but on the water a dramatic difference, and no more Guardian fault. So far the stainless part seems to be looking good, which is more than I can say for their aftermarket impellers which seem to destroy themselves after around 30 hours or 12 months. In hindsight I allowed myself to be distracted by the lack of Guardian cause code, thinking it to be something unusual that only the correct scan code could tell me. Lesson learned. In this situation I should have used the tool on the water and checked every single reading to make sure it was within range. Instead I only checked the readings on the hose. Hopefully this will help you out, although in the time it has taken me to reply you have probably either fixed it, bought a new boat or killed someone out of frustration!
  2. Thanks for your reply, and the links etc - all very helpful as usual thanks. So now Im getting closer here! Pulled the raw water pump. The sides look and feel fine to me. However both ends have some scouring and look like this. So while it's out I plan to fix that using this kit from Aftermarket Marine. I'll see what effect this has. thanks again for the advice - Ill report back
  3. The impellor was done about 8 months before I bought the boat, just the impellor apparently. But my understanding was that a worm impellor, in addition to being unlikely in that time as I mentioned, would cause overheating at low and high revs. I can idle / use the boat up to 3000 rpm all day long without the temperature budging (verified by the scan tool). That's why Im thinking pickup restrictions/corrosions - although the boat is trailered, no anti-foul so Im not sure how that can be either. Hmmm.
  4. OK, Im getting somewhere at last. Returned the scan tool to Rhinda, who agreed it was very faulty and sent me a new one. On the water the new one shows the block pressure does not exceed 4 to 5 psi max, even at 4000rpm. That's too low isnt it? The coolant temperature (closed cooling) sits at 159/160F except for when I do around 3000rpm or more for a sustained period, when it gradually creeps up to 163 to 165max but no more. At this time the riser tops are at around 140-150F (IR thermomoter), just too hot to be comfortable to the touch so a little too hot I think. And, now somewhat unsurprisingly, at between 3800-4200 (it varies) guardian cuts in, and cuts the motor back to idle - although leaves no reason code and somewhat bafflingly says overrev has been reached 48 times which corresponds to one 15second guardian event!. Anyway, at least I know why now. What is interesting is the old (faulty) Rhinda tool saw block pressures of 7psi at 1100rpm on the ear muffs. Maybe more pressure can be generated, despite whatever the cause, is while on the ear muffs than in the water? Although I would have thought the opposite to be true. Odd indeed. So with a working Rhinda tool, this narrows it down - 5psi isnt right I dont think? But, aside from trying everything, Im not quite sure where to take my first fix attempt: The guardian symptoms are unchanged even with a change of pressure sensor to the updated version. This fact, combined with the rising coolant temperature (although Im not actually sure if a mere 5 degrees is indicative of a problem), would suggest that while possible, the sensor is probably now one of the less likely causes. It could also be the sensor wiring, however a short or open I can understand, but a simply inaccurate reading off two different sensors has got to be highly improbable. I could buy a pressure gauge and plumb it in, but Im thinking this is not the top of the list for likely causes so Im inclined to leave that step for now and save my cash. I think the pump pressure really is around 4-5psi. So then, it could be the pump. Only thing with this is I know for a fact the impellor was replaced by a competent marina 10 months ago. Still, a possible cause but Im not too hopeful that in 10 months the pump could degrade to that extent even taking into account the annual replacement recommendation. I also believe a fried impellor typically causes overheats at low and high rpm. But maybe Im wrong - the pump isnt hard to pull apart and replace the impellor I assume, so I will do that anyway since technically it's due. But Im not really expecting the answer to be there unless my reasoning is flawed. The only other potential cause I can think of is a restricted intake path. Isn't it just a simple pipe to the sterndrive? How do I test for that? Although I have read posts about an o-ring restricting input flow - which brings me back to how do I test for flow - or is it a pull everything apart and inspect? Is that just the leg removed to inspect, or harder than that?
  5. It's hovering around 4-5 psi. At 1100 rpm it's 7 (using the new sensor), and continues to increase with rpm - I didnt go beyond 2000 on the ears. Yes I agree re the water, although I confess to being a little confused with the non-sticky faults. I get that non-sticky faults are active when the fault is there and disappear when the fault goes away or when the ignition is cycled. But I cant for the life of me fathom why they wouldn't appear in the fault history, especially if they are causing Guardian mode. Why do Mercruiser code the ECM like that, I mean are there any circumstances when you wouldnt want to see a non-sticky fault that has caused Guardian? Or have I got it wrong? The previously attached spreadsheet has my readings, but once the engine is warm and the dash gauge reads 175, the scan tool gives me 70c (and recorded 70c for Guardian overspeed 7 seconds) or 159F like you say. The history data records available power 75% and overspeed for 7 seconds, coolant 70c, block pressure 4.5. I am assuming the ECM records this data once and at the end of Guardian mode, hence the block pressure of 4.5, as the remaining data shows load 22% and manifold pressure 10.4 - none of that consistent with Guardian mode start at 4083rpm. So it would have taken me around 7 seconds to throttle right back enough for the alarm to stop, at which point these readings would have been about right. Anecdotally I did notice the dash gauge crept up to a needle's width above 175 (so it might be indicating 180 perhaps) only after guardian mode for overspeed had kicked in and I had throttled back and everything had returned to apparent normal. But I didnt think anything of this as there was no recorded warning, no double beeps, 180 ish is not overheating as far as I know, and the dash gauge is obviously not that accurate - of course a water test will confirm this but I mention it as the only thing I can see that isnt 100% as expected because the gauge doesnt normally move at all, although Ive only had the boat for a short while. ========= As an aside, in case you need some amusement, I got the Rinda tool two days ago. First day I recorded al the PCM readings and put them in the attached spreadsheet and had a good play around with it. Second day it intermittently said "error no comms". On reconnecting it twice mis-identifed the ECM as MEFI1 and MEF3. I also noticed an erratic available power and later a steady one of 4%, which clearly isnt right because that was at 1100 rpm - far more than 4%. Of course Rinda said the tool just displays what it is sent, and naturally Mercruiser said their ECM either works or it dies (so likely wouldnt run the engine, and certainly not well) and would not send bad or partial data. I became the man in the middle. The only bit I can check, the wires from the ECM to the scan tool socket, consist of 4 wires probably a foot long, two for power two for data and so are easy to confirm continuity - and overall battery - engine earth and power appear to be connected reliably, certainly the engine works without hesitation or any other strange symptoms, until Guardian mode overspeed (which I actually consider "normal" - the ECM is working as designed). Strange hey! On the third day, with key on engine off to eliminate interference as a cause, the tool failed to recognise the ECM at all, and couldnt choose between MEFI1 MEFI2 CEF3 (I think), all of which are wrong, and even told me the motor had 670 hours on it (I know it has 150 from earlier successful readings and the concurring dash). Telling me they have never before seen this fault and that the tool "shouldnt misread the ECM type" they got me to post the tool back (living in Australia Ive now spent an extra 25% of the tool cost on postage). And so now I wait again! So, Im having a hard time here, and if anyone wants to send me a nice cold beer to cheer me up it'd be welcome!
  6. Well, that didnt work too well! Got the updated black raw water pressure sensor. No difference. So I thought Id stop running blind and buy the Rinda scan tool. But so far, it hasnt been as effective as even my reading glasses! Scanning and fault history give me 94 (pitot), 75 (fuel), 119 (steering), 104 (sea temp), 130 (trim) - none of which I think I have or care about. Fault history gives me 9 - guardian mode (which of course I knew anyway) and 19 overspeed, which I am assuming is exceeding a limit imposed by Guardian mode (around 4000 rpm). Guardian mode indicates 7 seconds and available power of 75%. Of course this could be a genuine overspeed. However the rpm gauge concurs with the scan tool at 1000 and 2000 rpm, so the rev counter would have to be very badly out or stuck but only at higher rpms (indicated 4000+ rpm at around 25 knots - expected top speed more like 35knots on a 7 metre fibreglass with 6.2 MPI in it). And at the same time the boat would also have to be well overpropped since the WOT should be 4800-5200. So Ive discounted this. So all this doesnt tell me much at all really. But if I run the motor (again on the trailer) and gently set rpm around 1000, I suddenly see the available power fluctuating madly between 4% and around 70% (sometimes staying on 4%). In this state, I do not see any of the data stream values fluctuating abnormally. But to my thinking, this fluctuating available power reading isnt normal. However, I dont see any guardian mode associated with it, which I would expect to if the available power really was fluctuating like that. So maybe its a bad reading, a red herring? And then I thought Id found it. I went looking for loose wires and found either a loose or disconnected stern oil wire (cant tell which, it "came apart in my hand!"). But reconnecting it, the same power fluctuations can be made to appear. So I disconnected the earth wire completely, expecting to see 153 low drive lube, or similar. But no, just the same codes as above (in both sticky and non-sticky). Nothing extra. No alarm, no Guardian, no fault codes. Now I am really baffled. The data readings are attached anyway, in case anyone is good at solving puzzles :-) ========================================================================================================================================= Just to answer some previous posts - Battery connections look good - scan tool confirms good voltage. Oil pressure is around 40 and temperature 175 when the alarm comes on. No fluctuations at all even after a long ride. The oil is Mercruiser 25w40 unless the previous owner put half a bottle in there to look good (which I seriusly doubt). Engine is a 2003 Mercruiser 6.2 MPI Horizon ECM555. The boat planes easily (easier than my older but similar boat with a 5.7 Thunderbold carby motor in it).
  7. Thankyou again for all that info. Im certainly learning fast with your help! The diagnostic manual (service manual #36 I assume) has the wiring but doesnt seem to show any measurements. But I guess techs usually just swap out the sensor or use the PC to read the values. I wonder if the Rinda scan tool would do that, or just the PC software? The only odd thing with my symptoms is I dont hear any warning buzzer at all, intermittent, every 45 seconds or whatsoever and the boat will idle, plane, no wake, whatever without issue for as long as I like - all appears just fine until the continuous buzzer at 4200 rpm and the forced throttle down to idle. And I assume my buzzer is working based on the latter fact. I could possibly conclude the sensor is partially working I suppose, OK for low rpm but not enough for high rpm. Anyway, enough theory, Ill swap it out and let you know ! To answer your question. the boat is an Australian made Whittley Cruismaster, I doubt you see those over there, but it's 7 metres long and weighs around 2.6 metric tonnes. As another point of interest, more for amusement than anything, when I tested the boat on the water the owner insisted it should be used only with the sterndrive in the full down position. I never run my boat like this, but she was so insistent I just let it go as it wasnt important to me at the time. Thinking about it now, Ive never tried having incorrect trim (and the trim tabs may have been in a "less than optimal position"), that would possibly account for some of the reluctance to rev up past 4000 I guess, I hadnt really thoiught about it until this conversation - I must try it one day to see how much of a negative influence it has! The owner said they never reved the boat to 4000, which with hindsight I maybe can start to believe! Off to place my order :-) thanks again ....
  8. Thanks for that info. Can I ask a couple more questions, and you not take them as me questioning you at all !! Im the one asking, therefore it's me who doesnt know... When you say these are classic symptoms (which is just the experience/confirmation I was looking for), you're saying there would be typically no apparent problem (aside from a reduction in power to "protect" the engine I presume) from a shorted sensor, no intermittent warning beeper - until in excess of 4000rpm? I was a bit baffled by the lack of other warnings before the engine shuts itself down, but maybe the ECU senses it isnt overheating (it sits on 175 on the gauge) even though it apparently has no water pressure, but at 4200 decides enough is enough. Is that how it works and why it matches my symptoms - well single symptom? My curiosity aside, and doing something about your advice, taking a look yes the sensor is white as you predicted - mounted at the rear starboard side of the engine. I can surely pull it and test for a short though, or perhaps they dont fail that cleanly? Are there test paramaters if it isnt simply shorted? This is more a curiosity I might add, the white sensor will obviously need to be replaced at some stage if it has been superceeded. Its looking like I should take the punt on the sensor instead of buying the scan tool right now, although of course it'd also be useful in future. Thanks again for your reply, it was just what I was looking for instead of randomly throwing cash at the problem!
  9. My 2004 6.2 MPI fresh water cooled Mercruiser runs just fine up to 4200rpm (which it struggles to get to), at which point it shuts down to idle speed with a constant warning buzzer. Once the throttle is returned to neutral all is well again, until 4200rpm. Im thinking there can only be a few causes of these particular symptoms, or alternately the more common causes, and if so some specific test or new sensors I could try for a quick fix. Can the raw water pressure sensor cause this? Im not sure why it wouldnt warn at lower rpm, unless it only fails at higher pressures. I do know they commonly fail or get clogged up, so Im thinking it may be worth investigating if it can cause these symptoms. I should also note the sterndrive oil was at (but not below) the "ADD" mark, but I dont see this as a potential cause (but mention it because if I knew what was I wouldnt be posting!). thanks for any help/advice (PSI know the real answer is to get a scan tool or pay for diagnostics. Ill do that if I cant take an educated guess here).