Problem: Single cylinder Yanmar Diesel has been showing blue smoke lately. With the raw water cooling turned on (normal usage), the engine may or may not start. If starts, then it runs at lower RPM for the fuel setting. By shutting off the raw water, the engine starts easily, and runs great, with less smoke (however, this is not a good way to run a diesel or any other type liquid cooled engine!!) The exhaust through hull is about 6 - 12 inches abouve the water line; I don't know if there is a siphon break in any part of the line, and is used in salt water. Thanks, Bob
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coked elbow
Hello Bob: Sounds to me like a stopped up elbow.Exhaust gas can get thru but not liquid. How long since last cleanout? Also possible water lift muffler trbl,or exhaust hose. Let us know what fixes it Good luck red
Hello Bob: Sounds to me like a stopped up elbow.Exhaust gas can get thru but not liquid. How long since last cleanout? Also possible water lift muffler trbl,or exhaust hose. Let us know what fixes it Good luck red
Mysterious
Blue smoke is caused by burning oil, frequently the result of a blowby in the cylinders. However, if that were the case, I don't think it would be affected by whether the the raw water intake was open or not. The symptoms you describe sound like you have some breach in your water cooling system, allowing some water to seep into the cylinders. But then you would see white smoke (water vapor). Unfortunately, neither situation is particularly good, possibly requiring an overhaul. If the problem was a partially blocked exhaust system, it would balk at higher RPMs and emit black smoke. And it wouldn't matter whether you had your water line open. Is you engine sea water cooled, or do you have a "fresh water" cooled system (i.e with antifreeze). How old is your engine? Change your oil lately? Is it filled correctly? Does the oil have a milky appearance?
Blue smoke is caused by burning oil, frequently the result of a blowby in the cylinders. However, if that were the case, I don't think it would be affected by whether the the raw water intake was open or not. The symptoms you describe sound like you have some breach in your water cooling system, allowing some water to seep into the cylinders. But then you would see white smoke (water vapor). Unfortunately, neither situation is particularly good, possibly requiring an overhaul. If the problem was a partially blocked exhaust system, it would balk at higher RPMs and emit black smoke. And it wouldn't matter whether you had your water line open. Is you engine sea water cooled, or do you have a "fresh water" cooled system (i.e with antifreeze). How old is your engine? Change your oil lately? Is it filled correctly? Does the oil have a milky appearance?
Additional thoughts, based on replies
Thanks to both, now I believe I know how to troubleshoot this (piece by piece). The oil is a jet black, has been changed recently. I'm not sure about the 'cocked elbow'? Which elbow? One question I did not thinkn to ask is this: When the engine is running what should be full speed (about 5 kts), how much water should be coming out the exhaust? I observed another boat nearbye, and their exhaust resembled a lawn hose pouring out, where ours resembles a lawn hose being drained out. These numbers are not correct, but are relative comparision. If the other boat was pumping out 5 gpm on a 1" exhaust, then we were pouring out maybe 1 gpm (much less, but something). But I wonder if the "water lift" were clogged, then that would increase the back pressure. Hmm clogged with a sponge like material .. would pass gasses but have a problem with liquid. I have had auto diesels for years, but in Nigel Calders book on "Boatowners Mechanical etc" I see the raw water cooling parts company with autos real quick. I think what we need do is go into the system piece meal and check each component. I'm not sure about the siphon break part. Well, I told my son wanted to learn all about boats. Guess I am now .. thanks and will post the real answer .. Bob
Thanks to both, now I believe I know how to troubleshoot this (piece by piece). The oil is a jet black, has been changed recently. I'm not sure about the 'cocked elbow'? Which elbow? One question I did not thinkn to ask is this: When the engine is running what should be full speed (about 5 kts), how much water should be coming out the exhaust? I observed another boat nearbye, and their exhaust resembled a lawn hose pouring out, where ours resembles a lawn hose being drained out. These numbers are not correct, but are relative comparision. If the other boat was pumping out 5 gpm on a 1" exhaust, then we were pouring out maybe 1 gpm (much less, but something). But I wonder if the "water lift" were clogged, then that would increase the back pressure. Hmm clogged with a sponge like material .. would pass gasses but have a problem with liquid. I have had auto diesels for years, but in Nigel Calders book on "Boatowners Mechanical etc" I see the raw water cooling parts company with autos real quick. I think what we need do is go into the system piece meal and check each component. I'm not sure about the siphon break part. Well, I told my son wanted to learn all about boats. Guess I am now .. thanks and will post the real answer .. Bob
Elbow
Hello again: The elbow I was refering to is located on the aft end of the exhaust manifold, it loops up and down in a 180 deg turn and has the water injection hose tapped into it. As to the amount of water at exhaust,should come out in spurts about 3 seconds apart and look like a garden hose being turned off and on. This is the characteristics of a water lift muffler. Hope this helps Good luck red
Hello again: The elbow I was refering to is located on the aft end of the exhaust manifold, it loops up and down in a 180 deg turn and has the water injection hose tapped into it. As to the amount of water at exhaust,should come out in spurts about 3 seconds apart and look like a garden hose being turned off and on. This is the characteristics of a water lift muffler. Hope this helps Good luck red
Not enough information
Year and type of engine? Although mixing elbows should eventually be replaced (or at least sand blasted if not rusting through) and the raw cooling water path through the engine and hoses should be checked for restrictions from salt build up and solids which settle, I fail to see a connection with blue smoke...
Year and type of engine? Although mixing elbows should eventually be replaced (or at least sand blasted if not rusting through) and the raw cooling water path through the engine and hoses should be checked for restrictions from salt build up and solids which settle, I fail to see a connection with blue smoke...
Pump
Just for drill make sure your raw water pump is not binding up on you. It could be binding and seriously loading the engine until the belt starts to slip. Just a theory.
Just for drill make sure your raw water pump is not binding up on you. It could be binding and seriously loading the engine until the belt starts to slip. Just a theory.
Follow-Up to base note
OK, Traced out the entire exhaust system from stern discharge to water/ exhaust mixer, and the "U" pipe. No sign of obstruction. Used one of those plumbers spiral snakes. Nothing but bits of carbon. Remove flex hoses from 'baffled?' muffler (round, about 14" inches long, just above bilge) .. looked real clean. Didn't remove as some of the mounting screws appeared to fasten through the hull. Remove "U" hose from water mixer jacket to water / exhaust mixer. Clean as is the interior of the two ports. The only 'apparent' obstruction "may be" in the exhaust of the water mixer, which is clearly rusted bad enough to the rubberized water exhaust hose could not be renmoved without chancing destruction of same. Checked the 'exhaust' with screw driver tips and handles, andfound a 1" handel could be inserted about 1/4" into the outlet of the water mixer after scraping a bit of rust off the outlet port. Questions on the 'zinc' came up. no answer yet. This is the Yanmar SB8 single cyliner, type X cooling. Water comes from the pump, to a "T" in the head. Part of the water is diverted through the head and part can flow through a continuing hose to the water jacket. Water jacket is that piece on the rear of the engine that the water / mixer screws into. // Yes, did replace and reaffix everything otherwise disconnected // ;^) It has been described to me that the water flow shoild be like from a slow hose in spurts. It's doing that alright, but now with the water on, it 'hunts' up and down in RPM. Found that out Sunday coming into the mooring field, into a 10 kt wind wondering if the engine was going to slow down and to 0 rpm .. at least the anchor would still work .. i think ;^) I am wondering abot the water pump, and it's effects if it were not pumping enough volume, or if portions of the impeller blades did break off, where might they be now ?? However, if I recall my practical physics classm if the impeller blades were not making a good contact with the pump housing, then only negligible water would be pumped ?? Also, when the water is left off a few moments, and then turned back on, there is a time delay of about a minute, more/less before the engine slows down, implying "filling the system". The smoke is decidedlty whiter and more volume with the water on. like embarresingly bigger clouds ... Thanks Bob
OK, Traced out the entire exhaust system from stern discharge to water/ exhaust mixer, and the "U" pipe. No sign of obstruction. Used one of those plumbers spiral snakes. Nothing but bits of carbon. Remove flex hoses from 'baffled?' muffler (round, about 14" inches long, just above bilge) .. looked real clean. Didn't remove as some of the mounting screws appeared to fasten through the hull. Remove "U" hose from water mixer jacket to water / exhaust mixer. Clean as is the interior of the two ports. The only 'apparent' obstruction "may be" in the exhaust of the water mixer, which is clearly rusted bad enough to the rubberized water exhaust hose could not be renmoved without chancing destruction of same. Checked the 'exhaust' with screw driver tips and handles, andfound a 1" handel could be inserted about 1/4" into the outlet of the water mixer after scraping a bit of rust off the outlet port. Questions on the 'zinc' came up. no answer yet. This is the Yanmar SB8 single cyliner, type X cooling. Water comes from the pump, to a "T" in the head. Part of the water is diverted through the head and part can flow through a continuing hose to the water jacket. Water jacket is that piece on the rear of the engine that the water / mixer screws into. // Yes, did replace and reaffix everything otherwise disconnected // ;^) It has been described to me that the water flow shoild be like from a slow hose in spurts. It's doing that alright, but now with the water on, it 'hunts' up and down in RPM. Found that out Sunday coming into the mooring field, into a 10 kt wind wondering if the engine was going to slow down and to 0 rpm .. at least the anchor would still work .. i think ;^) I am wondering abot the water pump, and it's effects if it were not pumping enough volume, or if portions of the impeller blades did break off, where might they be now ?? However, if I recall my practical physics classm if the impeller blades were not making a good contact with the pump housing, then only negligible water would be pumped ?? Also, when the water is left off a few moments, and then turned back on, there is a time delay of about a minute, more/less before the engine slows down, implying "filling the system". The smoke is decidedlty whiter and more volume with the water on. like embarresingly bigger clouds ... Thanks Bob
White smoke
Hello Bob: The last part of your reply,seems to point to water getting into the cyclinder. Sounds like your a candidate for, at least a new head gasket. Hope it's that simple. A fairly easy job. Good luck red
Hello Bob: The last part of your reply,seems to point to water getting into the cyclinder. Sounds like your a candidate for, at least a new head gasket. Hope it's that simple. A fairly easy job. Good luck red
SB8
OK, we have exactly the same engine/same vintage. White smoke would generally be water, not oil. Last post regarding a new head gasket is worth following up first. Sounds like your raw water cooling sytem is generally OK. If you get water in your exhaust, the raw water pump has to be working. (Very easy item to check...). Assuming your thermostat is not fried, the delay before you get your "hunting" may simply be the time it takes your engine to warm up to operating temperature and the thermostat to open. The water now goes throught the engine block instead of bypassing it as when the engine is still cold, so it is only at this point in time that it would begin seeping into your combustion system. (One more hint to check/clean your water passages: remove the hoses of that "T-tube" you mentioned, and twist a long shank flat-bladed screwdriver SLOWLY into each opening as far as it will go. This will scrape some crud off the walls of the tubing, and through the straight tube you will be able to reach all the way toward the front to your engine zinc and retrieve a white "mushy" stuff if your zinc needs to be wire brushed). Unrelated: If yours is the original mixing elbow, it's probably pretty shot anyway, but not necessarily connected to the problem at hand. You can't check it's condition without removing it. If you do want to eventually change that elbow (You should replace the thermostat at the same time) message me first - I have just done it, and I would have some warnings/hints on how to best go about it, and I have made drawings as to how the parts disassemble/assemble which are much clearer then the engine manual which I also have.
OK, we have exactly the same engine/same vintage. White smoke would generally be water, not oil. Last post regarding a new head gasket is worth following up first. Sounds like your raw water cooling sytem is generally OK. If you get water in your exhaust, the raw water pump has to be working. (Very easy item to check...). Assuming your thermostat is not fried, the delay before you get your "hunting" may simply be the time it takes your engine to warm up to operating temperature and the thermostat to open. The water now goes throught the engine block instead of bypassing it as when the engine is still cold, so it is only at this point in time that it would begin seeping into your combustion system. (One more hint to check/clean your water passages: remove the hoses of that "T-tube" you mentioned, and twist a long shank flat-bladed screwdriver SLOWLY into each opening as far as it will go. This will scrape some crud off the walls of the tubing, and through the straight tube you will be able to reach all the way toward the front to your engine zinc and retrieve a white "mushy" stuff if your zinc needs to be wire brushed). Unrelated: If yours is the original mixing elbow, it's probably pretty shot anyway, but not necessarily connected to the problem at hand. You can't check it's condition without removing it. If you do want to eventually change that elbow (You should replace the thermostat at the same time) message me first - I have just done it, and I would have some warnings/hints on how to best go about it, and I have made drawings as to how the parts disassemble/assemble which are much clearer then the engine manual which I also have.
SOLVED: H27 w/ Yanmar diesel loses rpm's when raw
re: >Problem: Single cylinder Yanmar Diesel Shutting off the raw water cooling, the engine >starts easily, and runs great, with less smoke (however, this is not a good way to run a >diesel or any other type liqhuid cooled engine!!) Removed the old thermostat and the problem went away. New thermostat on order. Thanks to all with the suggestions and ideas. Bob
re: >Problem: Single cylinder Yanmar Diesel Shutting off the raw water cooling, the engine >starts easily, and runs great, with less smoke (however, this is not a good way to run a >diesel or any other type liqhuid cooled engine!!) Removed the old thermostat and the problem went away. New thermostat on order. Thanks to all with the suggestions and ideas. Bob
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