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Post by patryk221 on Jul 3, 2014 17:19:42 GMT
Cleaned the exhaust elbow still the same.. could it be that the prop is too big? Am out of ideas....tested by placing the boat into reverse slowly increasing revs on full power black smoke and a lot of diesel constantly thrown out through the exhaust
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Post by MalcolmP on Jul 3, 2014 17:46:41 GMT
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Post by patryk221 on Jul 3, 2014 19:22:18 GMT
Melcom if the valves were worn would she start first time? Would she run perfect with no smoke, even in high revs in neutral? This only happens when the engine is under high revs load if that makes sense, and unburned fuel is spit out:( the exhaust hole was around 25mm wonder if I cleaned it enough
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Post by MalcolmP on Jul 3, 2014 19:25:27 GMT
Melcom if the valves were worn would she start first time? Would she run perfect with no smoke, even in high revs in neutral? This only happens when the engine is under high revs load if that makes sense, and unburned fuel is spit out:( the exhaust hole was around 25mm wonder if I cleaned it enough Sorry don't know, but you seem to have explored other options and the symptoms do seem to correlate to me. Others with more diesel engine knowledge may hopefully add their views if the valves might be a culprit
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Post by ianqv on Jul 3, 2014 22:21:43 GMT
Hi Patryk, It won't be your prop. The fuel pump delivers varying amounts of fuel depending on how far open the throttle is. The timing is obviously controlled by the rotation of the pump pulley. Our early marine diesel are very primitive! The are almost no sensors or actuators (apart from temp and oil pressure). If diesel is coming out of the exhaust you have a base engine problem. If only to shut us up ( ) can you check the compressions? Remember diesel combusts under compression only. If you are getting diesel coming out of the exhaust - it has not been combusted correctly. Causes for this as follows: Crap fuel Exhaust restriction Inlet restriction Rings Valves Injector Fuel pump Obviously.... this is not a comprehensive list, but cracked blocks / heads etc are v rare! Its very hard to diagnose this end of the pc without data. Go on.... just humor us and check compressions. It will help us make the next step. I know it starts and runs, I'm guessing they could be border line! Easy to do... remove all 3 injectors, plug in an automotive DIESEL compression tester, crank over for the same amount of time for each check. Keep us posted... Best Regards Ian
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Post by ianqv on Jul 4, 2014 9:24:57 GMT
Compression spec.....
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Post by patryk221 on Jul 8, 2014 21:19:23 GMT
Ok after spending 4 hours with this sweet engine of mine have come to a conclusion that the issues might be an oversized/ too much pitch prop, compression is fine(checked) valves clearance spot on (checked) air intake checked clean as a baby's bottom, exhaust elbow cleaned (25-30mm bore) pumping plenty of water, injectors cleaned, all fuel filters changed, in neutral 3700rpm as per book which I have for that engine under load Only between 2600-2700rpm(2700 is max she will go) black smoke and unburned fuel chucked out of the exhaust last step is taking the head off and checking there but I certainly don't want to do that or New Engine:) thank to all that contributed this problem is a weird one apparently if fuel pump was out by one teeth you would get nocking noise and engine would not run properly mine does until you go over 2700rpm and starts first time
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Post by patryk221 on Jul 8, 2014 21:45:24 GMT
Symptoms of a wrongly matched propellor/engine/hull: An oversize propellor will mean the boat travels quite quickly at tickover, but as the throttle is opened does not pick up much more speed, and the engine labours rather than revving up - like a car starting off in too high a gear. Similarly an undersize prop will allow the engine to race, but not produce much speed
Characteristic signs of an overloaded diesel engine are excessive black smoke at cruising speed, exhaust temperatures beyond those specified by the manufacturer, and most importantly, an inability to reach full rated RPM at wide open throttle on a fully loaded boat with fuel and water tanks at capacity
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Post by ianqv on Jul 10, 2014 21:20:00 GMT
Hi Patryk Many thanks for all the feedback, and as you quite rightly say... this is a real weird one! I agree with what you say re the engine not revving due to the prop size. But perhaps something else may be up (in addition to the prop). If you are laboring the engine, you still should not get fuel (as a liquid) coming out of the exhaust. If you drive your car up a steep hill in the wrong gear, it will just slow down (and eventually stop) - you won't get fuel coming out of the exhaust pipe. PLEASE do keep us posted... apologies that we have not helped you solve the problem!
Best Regards
Ian
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Post by patryk221 on Nov 3, 2014 18:12:19 GMT
Update: prop pitch was an inch too much 16x11 instead of 16x10 problem resolved
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Post by sailbleu on Nov 4, 2014 4:14:33 GMT
Update: prop pitch was an inch too much 16x11 instead of 16x10 problem resolved Have been following this topic but did not join in as I felt I couldn't add anything sensible to this discussion. I do know something about diesel engines and like many on this board I do my own maintenance and all , but I've never heard of liquid fuel squirting out of the exhaust when putting the pedal to the metal. Unless the engine would run like a square which was not the case in this case. Ian listed up a number of possibilities in which each could make his own pick. But this update really supprises me , I was not aware of the fact that a wrong sized prop could be responsable for the mentioned problem. Could anyone give us the theory behind this phenomenon ? I'm so much interested in that , and I bet I'm not the only one. Regards
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Post by electricmonk on Nov 4, 2014 15:21:12 GMT
Sailblue,
The way the "throttle" works on an old style diesel (pre common rail) is nothing like the throttle on a petrol engine with a carburettor.
Petrol engine: The throttle is opened by the driver and acceleration pump introduces more fuel and the engine speeds up, as it speeds up the carburettor supplies more fuel air mixture - it depends on (mostly) the volume of air passing through the venturi- and actually NOT dependant on the throttle opening - except as volume maxes out dependant on the throttle opening the engine speed will level off - lets be clear I am not talking about the case where we rev the engine to destruction.
Diesel Engine: Has no venturi the driver sets the fuel supply by opening or setting a rack in the injection pump, this increases the amount of fuel delivered, the engine responds by speeding up until the fuel air mixture wont let it rev any higher (again we are not talking about the case where we let it rev to destruction).
IF the engine cannot reach the revs where the fuel air mixture is correct then there is an excess of fuel, this manifests its self as black smoke and unburnt fuel being passed through the exhaust system - why? because there is not enough air to burn it - we need more revs, but we don't have them these engines do not automatically adjust their fuel supply and there is no restriction on the air supply. Unlike the petrol engine where the fuel supply is automatically adjusted by the carburettor depending on the volume of air the diesel engine fuel supply is adjusted by the driver and if the engineering wont allow the diesel to reach sufficient revs/air volume then black smoke and problems ensue.
I'am sure we have all seen diesel cars and trucks belching out black smoke - its the same problem - overloaded - foot on the floor to high a gear- in a boat over propped and hence over fuelled.
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Post by patryk221 on Nov 4, 2014 16:49:04 GMT
Electrickmonk
SPOT on!! overload its amazing the whole engine now feels smooth glad I sorted this one out...one inch is a lot if you multiply it by 2500rpm=huge overload
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Post by electricmonk on Nov 4, 2014 18:46:53 GMT
Electrickmonk SPOT on!! overload its amazing the whole engine now feels smooth glad I sorted this one out...one inch is a lot if you multiply it by 2500rpm=huge overload A few observations For my sins in another life I used to process engineer diesel engines, and in yet another life I was involved in an engine reconditioning shop - long before the common rail was a twinkle in the designers eye. Diesels are quite simple machines but they must be matched to the load or all sorts of troubles ensue; for anyone who is interested the wide open throttle test under load is THE essential test when you inspect a diesel engine in a boat, if it pulls full revs without smoking, overheating or shaking itself to pieces then its probably OK - it could be underpropped but that is preferable to over proped (do the test in open water not tied up to the quay and run for an hour at full rated rpm). The big issues with marinised diesels apart from the loading issues are keeping them cool and well ventilated and supplying them with clean fuel. So it may sound a little perverse a contradiction even when I say they that most marine diesels die because they never reach operating temperature (raw water cooled examples) and are not run hard enough or long enough (all of them). The non ventilated ones tend to rust away.
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Post by Trevor on Nov 4, 2014 20:38:54 GMT
Electricmonk,
Really great explanation so many thanks!
Trevor
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Post by sailbleu on Nov 5, 2014 4:14:04 GMT
Nice to know we have an expert on board. Duly noted. Thanks electricmonk.
Regards
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Disralei
New Member
Posts: 4
Country: Australia
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Post by Disralei on Nov 6, 2014 10:55:54 GMT
I have no doubt that the exhaust elbow will be the culprit, I changes mine and I think the throat was in excess of 45mm, however the diesel being spat out may be something entirely different. as a matter of interest the exhaust elbows on Volvos should be changed every 5 years depending on use, you will find that the motor will run a whole lot quieter also.
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Post by sailbleu on Nov 6, 2014 12:56:55 GMT
Disralei , could it be that you missed something in this discussion ? I believe it was the size of the prop , not the exhaust elbow. But you are correct that the elbow is a pain in the b*tt/exhaust Four years ago I had the impression less cooling water was gushing out of the exhaust. During the next winter on the hard I removed the elbow and found this. A view on the engine exhaust Deposits of soot , not just here , also in the elbow Since then , on a regular basis , I boost the engine's revs to blow out the soot. But there's more In the white circle you see the hole (there are two opposite of each other) that was also clogged . Less cooling for the engine. With a long and thin screwdriver I managed to brig the holes to the right size again. Running the chance of strolling too much off topic maybe a few words of caution.A picture taken back then of the removed waterintake of the elbow. This is where the cooling raw water is being guided in the elbow. While removing the hose of the intake so the elbow could come off a piece broke off leaving me little to no material to put the howe back on. So please be gentle when you take it off. The part was cleaned to take a good picture of the inside . It seemed to be completely eaten or rusted away. By what I heard this is a kind of poreus cast iron that suffer alot by salt water. Or is there another reason ? It was obvious , I couldn't use this part anymore. Have a look at the new price , it's part number 29. www.marinepartseurope.com/nl/volvo-penta-explosietekening-7746710-25-2850.aspxAlso check number 23,...................still breathing ? Enough to get me moving and make a diy one. It does the job. As by wonder i found (after given a hint by someone) a brand new elbow on a secondhand site. Only 50 Euro's or so . Now , almost 5 years later , I still have 2 elbows . A few weeks ago , I coincidentely removed the elbow to check things up. The inside was scaled and oxidized again , water holes where narrower once more so up came the screwdriver. Who says a boat doesn't need maintenance Regards
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Post by electricmonk on Nov 6, 2014 17:48:52 GMT
The Volvo elbow is a known weakness, there are aftermarket suppliers who make them from stainless, but they still need checking regularly, the best thing for cleaning them is a DIY sand blaster www.piecesbateaux.com/,us,4,PAM-52-P1223.cfm An observation: in the images above of the exhaust port there is a lot of unburnt fuel and oil in there, as well as a lot of soot - lets be clear there should be no soot, fuel or oil; if the engine is working (worked) properly, you should only see a light grey "ash" lining the exhaust tracts. For anyone who is interested How to reduce the amount of soot and unburnt fuel in the exhaust: open the throttle slowly, try to match the throttle to the revs so you don't over-fuel the engine as it accelerates - the engine does not automatically adjust the fuel air mixture - so help it out. Reducing over fueling does many things all of which are beneficial, it reduces the amount of unburnt fuel in the exhaust, reduces the soot deposits in the exhaust elbow, reduces the dilution of the lubricating oil round the piston rings, extending their life and reduces the dilution of the lubricating oil in the sump which also extends the life of the engine as a whole. It also cuts down on the black stains round the exhaust pipe. We have all seen it, boat approaches berth at 6kts skipper slams it into reverse and revs the engine as high as it can go astern, boat slows to halt rapidly in a cloud of black smoke, skipper then cuts the engine, thus ensuring that the oil in the piston rings is washed away and the sump oil is diluted; diesel engineer watching from afar rubs his hands in glee - another engine and gearbox rebuild in the making.
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Post by sailbleu on Nov 6, 2014 19:49:03 GMT
Hey Electricmonk,
the reasons of these deposits - in my humble opinion anyway - is because my VP has always used some oil . Be it that the last few years it became less. Yes , it's decreasing . But there's also the fact that I never run my engine above 2000 rpm . More ,....my cruising revs are around 1700 rpm. Therefor I get alot of accumulation in the exhaust. I know ,low revs give glazing of the cilinders and so on . I try to treat my engine as if it was my baby.Such a vital part of the boat is it not ?
Regards
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Post by rodgerg on Nov 6, 2014 20:14:28 GMT
Very interesting thread this which has helped re-assure me that advice I was given must be correct. I was having overheating problems. i was told to run my engine harder. I have and I have never had the same problem since. Side effect though...I get places faster.
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Post by electricmonk on Nov 6, 2014 21:19:24 GMT
Hey Electricmonk, the reasons of these deposits - in my humble opinion anyway - is because my VP has always used some oil . Be it that the last few years it became less. Yes , it's decreasing . But there's also the fact that I never run my engine above 2000 rpm . More ,....my cruising revs are around 1700 rpm. Therefor I get alot of accumulation in the exhaust. I know ,low revs give glazing of the cilinders and so on . I try to treat my engine as if it was my baby.Such a vital part of the boat is it not ? Regards Yes it is a vital part of the boat and to keep it in good condition I would recommend you run it max rated continuous RPM for a least 1 hour (continuous) in every 50, it will last longer. Max RPM on that engine is 3,900 max rated continuous will be around 3,500 (check the user manual) you should try to cruise at 75- 80% of max rpm (somewhere around 2,800-3,000rpm); everything benefits, the engine runs at its correct temperature, the exhaust cleans its self, valves don't coke up, extra boat speed keeps the fouling down etc etc. Your oil consumption is (IMHO) partly due to the fact that engine has never been run in, but its getting there, that said it may wear out before its run in! (many do its quite possible and easy to kill then with kindness), I would definitely run it harder and longer it will reward you with more power, smoother running and less breakdowns. Clean oil, clean fuel and gentle acceleration is the way to extract maximum life from a diesel - not low rpm. Never seen glazed bores due to slow running (for glazed read worn out) - but have read about it on forums, (lots of diesel plant spends most of its life at idling speeds and they survive for many thousands of hours - but when they're not idling they are at 75 or more % of full load - there's a clue there, and most plant is regularly serviced), I have seen lots of pistons with the rings stuck in them so there is no compression, and bores worn out due to high engine hours or diluted and/or dirty oil; sumps full of bitumen - could have been oil back in the mists of time - but we had to remove it with a chisel - sumps full of water, sumps full of diesel, sumps full of air, and the owners of these wrecks claim to have had them recently serviced - connecting rods bent and cylinder heads cracked due to hydraulic lock, it never ceased to amaze me how ingenious some owners were and how determined they were to find new and inventive ways of killing their engines. I have to say I am impressed by the Jeanneau engine installations they are hard to fault, but some boat builders obviously have no idea and their criteria is if the engine makes a noise and propeller goes round then the jobs a good un. Many don't (didn't) appreciate the need for forced engine space ventilation or providing access for servicing, anti siphon valves, exhaust traps, goose necks, fuel water traps etc - yes you can leave all that equipment out and the engine will "work" sort of; and they were more than willing to argue from a position of absolute ignorance which I found very worrying.
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