Just had the heat transfer bundle replaced because of overheating of my Yanmar 29HP 3YM30. Now, when running at 2800 rpms, the engine cuts down to less than 1000 and runs extremely rough- sputtering and coughing. Changed fuel filters, but the problem remains, even after 30 sec at 2800 rpms in idle. Anyone experience this and know what the remedy might be?
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Sound Like Warranty Work is Still in Order
Contact Hunter Marine or the dealer to straighten this out. I wouldn't get involved or else the "repairer" will drop it because it will become finger-pointing.
Contact Hunter Marine or the dealer to straighten this out. I wouldn't get involved or else the "repairer" will drop it because it will become finger-pointing.
Did it run OK before?
Did it run OK before the new heat eachanger? Did you overheat the engine before the new heat exchanger was installed?
Did it run OK before the new heat eachanger? Did you overheat the engine before the new heat exchanger was installed?
Fuel supply issue
This sounds like a fuel supply issue. There is enough fuel in the system to run the engine for a short period of time, at which point the engine struggles for a fuel supply. I guess it is remotely possible that your previously overheating engine fouled the fuel injectors. My best guess though is the fuel filter body on the top left side of the engine. There is a seconday filter in there. It could be fouled or the bleed screw on the top could be leaking air into the fuel lines. Regardless I would make sure that the fuel system is bled out properly. In the past I have hand filled the fuel filter body assembly on the engine, not the primary Racor filter, and run the engine. If it runs fine until the fuel is gone then you can probably eliminate the fuel pump this seconday filter. I do the same thing again at the primary, Racor, filter assembly. If it is still fine then I would suspect your pick-up line in the fuel tank itself. Do you use an anti-growth additive in you diesel fuel? I would also check the engine linkage cables. Go down below and have someone start the engine in neutral. Run it up to speed while you watch the cable at the engine (Just above the transmission in the back of the engine). You may find it is slipping there. Follow the entire fuel line. You may find a kink or a pinched section. BTW. When I had my cooling core replaced for the same overheating problem on my 3YM30 the positive wire to my alternator was not attached securely. The alternator had to be removed to access the core. It arced and sparked until it burnt out and no longer was charging my batteries. Good luck Andy
This sounds like a fuel supply issue. There is enough fuel in the system to run the engine for a short period of time, at which point the engine struggles for a fuel supply. I guess it is remotely possible that your previously overheating engine fouled the fuel injectors. My best guess though is the fuel filter body on the top left side of the engine. There is a seconday filter in there. It could be fouled or the bleed screw on the top could be leaking air into the fuel lines. Regardless I would make sure that the fuel system is bled out properly. In the past I have hand filled the fuel filter body assembly on the engine, not the primary Racor filter, and run the engine. If it runs fine until the fuel is gone then you can probably eliminate the fuel pump this seconday filter. I do the same thing again at the primary, Racor, filter assembly. If it is still fine then I would suspect your pick-up line in the fuel tank itself. Do you use an anti-growth additive in you diesel fuel? I would also check the engine linkage cables. Go down below and have someone start the engine in neutral. Run it up to speed while you watch the cable at the engine (Just above the transmission in the back of the engine). You may find it is slipping there. Follow the entire fuel line. You may find a kink or a pinched section. BTW. When I had my cooling core replaced for the same overheating problem on my 3YM30 the positive wire to my alternator was not attached securely. The alternator had to be removed to access the core. It arced and sparked until it burnt out and no longer was charging my batteries. Good luck Andy
fuel supply
The engine had overheated before the exchange, which is why I eventually found out that this engine can have this bundle problem that causes overheating. Andy, I changed both the raycor and the secondary fuel filters and bled the lines of air and still no change, which is the reason for the original inquiry. The engine had run ok before the bundle exchange. This loss of rpms only occurred after the exchange- and on the first day out after the exchange. Could just be coincidence... If it's in the fuel pick up line, say at the tank, what is the remedy?
The engine had overheated before the exchange, which is why I eventually found out that this engine can have this bundle problem that causes overheating. Andy, I changed both the raycor and the secondary fuel filters and bled the lines of air and still no change, which is the reason for the original inquiry. The engine had run ok before the bundle exchange. This loss of rpms only occurred after the exchange- and on the first day out after the exchange. Could just be coincidence... If it's in the fuel pick up line, say at the tank, what is the remedy?
Fuel tank
I have not had the need to access my fuel tank from the inside. You may be able to have your fuel polished (see archives) and that might clear the problem if your issue is sludge on the bottom of the tank. I really do not think this is the problem though. It would manifest itself as continually clogging primary filters before the pickup itself clogged. The fuel pickup sits a little off the bottom of the tank so a small amount of sludge in there would not immediatley clog the system. Stupid question: is the fuel shutoff valve opened all of the way? It is located at the tank and is accessible through the fuel tank port in the rear port cockpit locker. My story about the alternator wire was to point out that with the core being changed out the engine had a lot of things moved around. Maybe everything was not put back exactly as before... Andy
I have not had the need to access my fuel tank from the inside. You may be able to have your fuel polished (see archives) and that might clear the problem if your issue is sludge on the bottom of the tank. I really do not think this is the problem though. It would manifest itself as continually clogging primary filters before the pickup itself clogged. The fuel pickup sits a little off the bottom of the tank so a small amount of sludge in there would not immediatley clog the system. Stupid question: is the fuel shutoff valve opened all of the way? It is located at the tank and is accessible through the fuel tank port in the rear port cockpit locker. My story about the alternator wire was to point out that with the core being changed out the engine had a lot of things moved around. Maybe everything was not put back exactly as before... Andy
Fuel tank
I have not had the need to access my fuel tank from the inside. You may be able to have your fuel polished (see archives) and that might clear the problem if your issue is sludge on the bottom of the tank. I really do not think this is the problem though. It would manifest itself as continually clogging primary filters before the pickup itself clogged. The fuel pickup sits a little off the bottom of the tank so a small amount of sludge in there would not immediatley clog the system. Stupid question: is the fuel shutoff valve opened all of the way? It is located at the tank and is accessible through the fuel tank port in the rear port cockpit locker. My story about the alternator wire was to point out that with the core being changed out the engine had a lot of things moved around. Maybe everything was not put back exactly as before... Andy
I have not had the need to access my fuel tank from the inside. You may be able to have your fuel polished (see archives) and that might clear the problem if your issue is sludge on the bottom of the tank. I really do not think this is the problem though. It would manifest itself as continually clogging primary filters before the pickup itself clogged. The fuel pickup sits a little off the bottom of the tank so a small amount of sludge in there would not immediatley clog the system. Stupid question: is the fuel shutoff valve opened all of the way? It is located at the tank and is accessible through the fuel tank port in the rear port cockpit locker. My story about the alternator wire was to point out that with the core being changed out the engine had a lot of things moved around. Maybe everything was not put back exactly as before... Andy
Aside from contaminated fuel.....
...which will most certainly cause this kind of problem, air infiltration into the fuel supply line can cause these same symptoms. The suction side of the fuel pump can draw air into the fuel line mixing it with the fuel to form tiny bubbles which greatly affect the spray patterns of the injectors. A very easy test for this is to replace the flexible fuel line between the supply pump and injection pump with a transparent fuel line. This will give a 'window' to view the fuel as it passes. If small bubbles are noted, this is your problem. Check all connections between the suction side of the fuel pump and the fuel tank.
...which will most certainly cause this kind of problem, air infiltration into the fuel supply line can cause these same symptoms. The suction side of the fuel pump can draw air into the fuel line mixing it with the fuel to form tiny bubbles which greatly affect the spray patterns of the injectors. A very easy test for this is to replace the flexible fuel line between the supply pump and injection pump with a transparent fuel line. This will give a 'window' to view the fuel as it passes. If small bubbles are noted, this is your problem. Check all connections between the suction side of the fuel pump and the fuel tank.
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